(Slip Opinion)              OCTOBER TERM, 2009                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

             UNITED STATES v. COMSTOCK ET AL.

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
                 THE FOURTH CIRCUIT

    No. 08–1224. Argued January 12, 2010—Decided May 17, 2010
Federal law allows a district court to order the civil commitment of a
  mentally ill, sexually dangerous federal prisoner beyond the date he
  would otherwise be released. 18 U. S. C. §4248. The Government in
  stituted civil-commitment proceedings under §4248 against respon
  dents, each of whom moved to dismiss on the ground, inter alia, that,
  in enacting the statute, Congress exceeded its powers under the Nec
  essary and Proper Clause, U. S. Const., Art. I, §8, cl. 18. Agreeing,
  the District Court granted dismissal, and the Fourth Circuit affirmed
  on the legislative-power ground.
Held: The Necessary and Proper Clause grants Congress authority suf
 ficient to enact §4248. Taken together, five considerations compel
 this conclusion. Pp. 5–22.
    (1) The Clause grants Congress broad authority to pass laws in fur
 therance of its constitutionally enumerated powers. It makes clear
 that grants of specific federal legislative authority are accompanied
 by broad power to enact laws that are “convenient, or useful” or “con
 ducive” to the enumerated power’s “beneficial exercise,” e.g.,
 McCulloch v. Maryland, 4 Wheat. 316, 413, 418, and that Congress
 can “legislate on that vast mass of incidental powers which must be
 involved in the constitution,” id., at 421. In determining whether the
 Clause authorizes a particular federal statute, there must be “means
 ends rationality” between the enacted statute and the source of fed
 eral power. Sabri v. United States, 541 U. S. 600, 605. The Constitu
 tion “addresse[s]” the “choice of means” “primarily . . . to the judg
 ment of Congress. If it can be seen that the means adopted are really
 calculated to attain the end, the degree of their necessity, the extent
 to which they conduce to the end, the closeness of the relationship be
 tween the means adopted and the end to be attained, are matters for
2                   UNITED STATES v. COMSTOCK

                                  Syllabus

    congressional determination alone.” Burroughs v. United States, 290
    U. S. 534, 547–548. Thus, although the Constitution nowhere grants
    Congress express power to create federal crimes beyond those specifi
    cally enumerated, to punish their violation, to imprison violators, to
    provide appropriately for those imprisoned, or to maintain the secu
    rity of those who are not imprisoned but who may be affected by the
    federal imprisonment of others, Congress possesses broad authority
    to do each of those things under the Clause. Pp. 5–9.
       (2) Congress has long been involved in the delivery of mental
    health care to federal prisoners, and has long provided for their civil
    commitment. See, e.g., Act of Mar. 3, 1855, 10 Stat. 682; Insanity De
    fense Reform Act of 1984, 18 U. S. C. §§4241–4247. A longstanding
    history of related federal action does not demonstrate a statute’s con
    stitutionality, see, e.g., Walz v. Tax Comm’n of City of New York, 397
    U. S. 664, 678, but can be “helpful in reviewing the substance of a
    congressional statutory scheme,” Gonzales v. Raich, 545 U. S. 1, 21,
    and, in particular, the reasonableness of the relation between the
    new statute and pre-existing federal interests. Section 4248 differs
    from earlier statutes in that it focuses directly upon persons who, due
    to a mental illness, are sexually dangerous. Many of these individu
    als, however, were likely already subject to civil commitment under
    §4246, which, since 1949, has authorized the postsentence detention
    of federal prisoners who suffer from a mental illness and who are
    thereby dangerous (whether sexually or otherwise). The similarities
    between §4246 and §4248 demonstrate that the latter is a modest
    addition to a longstanding federal statutory framework. Pp. 9–14.
       (3) There are sound reasons for §4248’s enactment. The Federal
    Government, as custodian of its prisoners, has the constitutional
    power to act in order to protect nearby (and other) communities from
    the danger such prisoners may pose. Moreover, §4248 is “reasonably
    adapted” to Congress’ power to act as a responsible federal custodian.
    United States v. Darby, 312 U. S. 100, 121. Congress could have rea
    sonably concluded that federal inmates who suffer from a mental ill
    ness that causes them to “have serious difficulty in refraining from
    sexually violent conduct,” §4247(a)(6), would pose an especially high
    danger to the public if released. And Congress could also have rea
    sonably concluded that a reasonable number of such individuals
    would likely not be detained by the States if released from federal
    custody. Congress’ desire to address these specific challenges, taken
    together with its responsibilities as a federal custodian, supports the
    conclusion that §4248 satisfies “review for means-end rationality,”
    Sabri, supra, at 605. Pp. 14–16.
       (4) Respondents’ contention that §4248 violates the Tenth Amend
    ment because it invades the province of state sovereignty in an area
                      Cite as: 560 U. S. ____ (2010)                      3

                                 Syllabus

  typically left to state control is rejected. That Amendment does not
  “reserve to the States” those powers that are “delegated to the United
  States by the Constitution,” including the powers delegated by the
  Necessary and Proper Clause. See, e.g., New York v. United States,
  505 U. S. 144, 159. And §4248 does not “invade” state sovereignty,
  but rather requires accommodation of state interests: Among other
  things, it directs the Attorney General to inform the States where the
  federal prisoner “is domiciled or was tried” of his detention, §4248(d),
  and gives either State the right, at any time, to assert its authority
  over the individual, which will prompt the individual’s immediate
  transfer to State custody, §4248(d)(1). In Greenwood v. United
  States, 350 U. S. 366, 375–376, the Court rejected a similar challenge
  to §4248’s predecessor, the 1949 statute described above. Because
  the version of the statute at issue in Greenwood was less protective of
  state interests than §4248, a fortiori, the current statute does not in
  vade state interests. Pp. 16–18.
    (5) Section 4248 is narrow in scope. The Court rejects respondents’
  argument that, when legislating pursuant to the Necessary and
  Proper Clause, Congress’ authority can be no more than one step re
  moved from a specifically enumerated power. See, e.g., McCulloch,
  supra, at 417. Nor will the Court’s holding today confer on Congress
  a general “police power, which the Founders denied the National
  Government and reposed in the States.” United States v. Morrison,
  529 U. S. 598, 618. Section §4248 has been applied to only a small
  fraction of federal prisoners, and its reach is limited to individuals al
  ready “in the custody of the” Federal Government, §4248(a). Thus,
  far from a “general police power,” §4248 is a reasonably adapted and
  narrowly tailored means of pursuing the Government’s legitimate in
  terest as a federal custodian in the responsible administration of its
  prison system. See New York, supra, at 157. Pp. 18–22.
    The Court does not reach or decide any claim that the statute or its
  application denies equal protection, procedural or substantive due
  process, or any other constitutional rights. Respondents are free to
  pursue those claims on remand, and any others they have preserved.
  P. 22.
551 F. 3d 274, reversed and remanded.

   BREYER, J., delivered the opinion of the Court, in which ROBERTS,
C. J., and STEVENS, GINSBURG, and SOTOMAYOR, JJ., joined. KENNEDY,
J., and ALITO, J., filed opinions concurring in the judgment. THOMAS, J.,
filed a dissenting opinion, in which SCALIA, J., joined in all but Part III–
A–1–b.
                       Cite as: 560 U. S. ____ (2010)                              1

                            Opinion of the Court

    NOTICE: This opinion is subject to formal revision before publication in the
    preliminary print of the United States Reports. Readers are requested to
    notify the Reporter of Decisions, Supreme Court of the United States, Wash
    ington, D. C. 20543, of any typographical or other formal errors, in order
    that corrections may be made before the preliminary print goes to press.


SUPREME COURT OF THE UNITED STATES
                                  _________________

                                  No. 08–1224
                                  _________________


     UNITED STATES, PETITIONER v. GRAYDON 

           EARL COMSTOCK, JR., ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FOURTH CIRCUIT

                                [May 17, 2010]


  JUSTICE BREYER delivered the opinion of the Court.
  A federal civil-commitment statute authorizes the De
partment of Justice to detain a mentally ill, sexually
dangerous federal prisoner beyond the date the prisoner
would otherwise be released. 18 U. S. C. §4248. We have
previously examined similar statutes enacted under state
law to determine whether they violate the Due Process
Clause. See Kansas v. Hendricks, 521 U. S. 346, 356–358
(1997); Kansas v. Crane, 534 U. S. 407 (2002). But this
case presents a different question. Here we ask whether
the Federal Government has the authority under Article I
of the Constitution to enact this federal civil-commitment
program or whether its doing so falls beyond the reach of a
government “of enumerated powers.” McCulloch v. Mary
land, 4 Wheat. 316, 405 (1819). We conclude that the
Constitution grants Congress the authority to enact §4248
as “necessary and proper for carrying into Execution” the
powers “vested by” the “Constitution in the Government of
the United States.” Art. I, §8, cl. 18.
                            I
  The federal statute before us allows a district court to
2              UNITED STATES v. COMSTOCK

                     Opinion of the Court

order the civil commitment of an individual who is cur
rently “in the custody of the [Federal] Bureau of Prisons,”
§4248, if that individual (1) has previously “engaged or
attempted to engage in sexually violent conduct or child
molestation,” (2) currently “suffers from a serious mental
illness, abnormality, or disorder,” and (3) “as a result of”
that mental illness, abnormality, or disorder is “sexually
dangerous to others,” in that “he would have serious diffi
culty in refraining from sexually violent conduct or child
molestation if released.” §§4247(a)(5)–(6).
   In order to detain such a person, the Government (act
ing through the Department of Justice) must certify to a
federal district judge that the prisoner meets the condi
tions just described, i.e., that he has engaged in sexually
violent activity or child molestation in the past and that
he suffers from a mental illness that makes him corre
spondingly dangerous to others. §4248(a). When such a
certification is filed, the statute automatically stays the
individual’s release from prison, ibid., thereby giving the
Government an opportunity to prove its claims at a hear
ing through psychiatric (or other) evidence, §§4247(b)–(c),
4248(b). The statute provides that the prisoner “shall be
represented by counsel” and shall have “an opportunity” at
the hearing “to testify, to present evidence, to subpoena
witnesses on his behalf, and to confront and cross
examine” the Government’s witnesses. §§4247(d), 4248(c).
   If the Government proves its claims by “clear and con
vincing evidence,” the court will order the prisoner’s con
tinued commitment in “the custody of the Attorney Gen
eral,” who must “make all reasonable efforts to cause” the
State where that person was tried, or the State where he
is domiciled, to “assume responsibility for his custody,
care, and treatment.” §4248(d); cf. Sullivan v. Freeman,
944 F. 2d 334, 337 (CA7 1991). If either State is willing to
assume that responsibility, the Attorney General “shall
release” the individual “to the appropriate official” of that
                 Cite as: 560 U. S. ____ (2010)            3

                     Opinion of the Court

State. §4248(d). But if, “notwithstanding such efforts,
neither such State will assume such responsibility,” then
“the Attorney General shall place the person for treatment
in a suitable [federal] facility.” Ibid.; cf. §4247(i)(A).
   Confinement in the federal facility will last until either
(1) the person’s mental condition improves to the point
where he is no longer dangerous (with or without appro
priate ongoing treatment), in which case he will be re
leased; or (2) a State assumes responsibility for his cus
tody, care, and treatment, in which case he will be
transferred to the custody of that State. §§4248(d)(1)–(2).
The statute establishes a system for ongoing psychiatric
and judicial review of the individual’s case, including
judicial hearings at the request of the confined person at
six-month intervals. §§4247(e)(1)(B), (h).
   In November and December 2006, the Government
instituted proceedings in the Federal District Court for the
Eastern District of North Carolina against the five re
spondents in this case. Three of the five had previously
pleaded guilty in federal court to possession of child por
nography, see 507 F. Supp. 2d 522, 526, and n. 2 (2007);
§2252A(a), and the fourth had pleaded guilty to sexual
abuse of a minor, see United States v. Vigil, No.
1:99CR00509–001 (D NM, Jan. 26, 2000); §§1153, 2243(a).
With respect to each of them, the Government claimed
that the respondent was about to be released from federal
prison, that he had engaged in sexually violent conduct or
child molestation in the past, and that he suffered from a
mental illness that made him sexually dangerous to oth
ers. App. 38–40, 44–52. During that same time period,
the Government instituted similar proceedings against the
fifth respondent, who had been charged in federal court
with aggravated sexual abuse of a minor, but was found
mentally incompetent to stand trial. See id., at 41–43;
United States v. Catron, No. 04–778 (D Ariz., Mar. 27,
2006); §4241(d).
4              UNITED STATES v. COMSTOCK

                     Opinion of the Court

   Each of the five respondents moved to dismiss the civil
commitment proceeding on constitutional grounds. They
claimed that the commitment proceeding is, in fact, crimi
nal, not civil, in nature and consequently that it violates
the Double Jeopardy Clause, the Ex Post Facto Clause,
and the Sixth and Eighth Amendments. 507 F. Supp. 2d,
at 528. They claimed that the statute denies them sub
stantive due process and equal protection of the laws.
Ibid. They claimed that it violates their procedural due
process rights by allowing a showing of sexual dangerous
ness to be made by clear and convincing evidence, instead
of by proof beyond a reasonable doubt. Ibid. And, finally,
they claimed that, in enacting the statute, Congress ex
ceeded the powers granted to it by Art. I, §8 of the Consti
tution, including those granted by the Commerce Clause
and the Necessary and Proper Clause. 507 F. Supp. 2d, at
528–529.
   The District Court, accepting two of the respondents’
claims, granted their motion to dismiss. It agreed with
respondents that the Constitution requires proof beyond a
reasonable doubt, id., at 551–559 (citing In re Winship,
397 U. S. 358 (1970)), and it agreed that, in enacting the
statute, Congress exceeded its Article I legislative powers,
507 F. Supp. 2d, at 530–551. On appeal, the Court of
Appeals for the Fourth Circuit upheld the dismissal on
this latter, legislative-power ground. 551 F. 3d 274, 278–
284 (2009). It did not decide the standard-of-proof ques
tion, nor did it address any of respondents’ other constitu
tional challenges. Id., at 276, n. 1.
   The Government sought certiorari, and we granted its
request, limited to the question of Congress’ authority
under Art. I, §8 of the Constitution. Pet. for Cert. i. Since
then, two other Courts of Appeals have considered that
same question, each deciding it in the Government’s favor,
thereby creating a split of authority among the Circuits.
See United States v. Volungus, 595 F. 3d 1 (CA1 2010);
                 Cite as: 560 U. S. ____ (2010)            5

                     Opinion of the Court

United States v. Tom, 565 F. 3d 497 (CA8 2009).
                               II
   The question presented is whether the Necessary and
Proper Clause, Art. I, §8, cl. 18, grants Congress authority
sufficient to enact the statute before us. In resolving that
question, we assume, but we do not decide, that other
provisions of the Constitution—such as the Due Process
Clause—do not prohibit civil commitment in these circum
stances. Cf. Hendricks, 521 U. S. 346; Addington v. Texas,
441 U. S. 418 (1979). In other words, we assume for ar
gument’s sake that the Federal Constitution would permit
a State to enact this statute, and we ask solely whether
the Federal Government, exercising its enumerated pow
ers, may enact such a statute as well. On that assump
tion, we conclude that the Constitution grants Congress
legislative power sufficient to enact §4248. We base this
conclusion on five considerations, taken together.
   First, the Necessary and Proper Clause grants Congress
broad authority to enact federal legislation. Nearly 200
years ago, this Court stated that the Federal “[G]overn
ment is acknowledged by all to be one of enumerated
powers,” McCulloch, 4 Wheat., at 405, which means that
“[e]very law enacted by Congress must be based on one or
more of” those powers, United States v. Morrison, 529
U. S. 598, 607 (2000). But, at the same time, “a govern
ment, entrusted with such” powers “must also be en
trusted with ample means for their execution.”
McCulloch, 4 Wheat., at 408. Accordingly, the Necessary
and Proper Clause makes clear that the Constitution’s
grants of specific federal legislative authority are accom
panied by broad power to enact laws that are “convenient,
or useful” or “conducive” to the authority’s “beneficial
exercise.” Id., at 413, 418; see also id., at 421 (“[Congress
can] legislate on that vast mass of incidental powers which
must be involved in the constitution . . .”). Chief Justice
6              UNITED STATES v. COMSTOCK

                     Opinion of the Court

Marshall emphasized that the word “necessary” does not
mean “absolutely necessary.” Id., at 413–415 (emphasis
deleted); Jinks v. Richland County, 538 U. S. 456, 462
(2003) (“[W]e long ago rejected the view that the Neces
sary and Proper Clause demands that an Act of Congress
be ‘ “absolutely necessary” ’ to the exercise of an enumer
ated power”). In language that has come to define the
scope of the Necessary and Proper Clause, he wrote:
    “Let the end be legitimate, let it be within the scope of
    the constitution, and all means which are appropriate,
    which are plainly adapted to that end, which are not
    prohibited, but consist with the letter and spirit of the
    constitution, are constitutional.” McCulloch, supra, at
    421.
   We have since made clear that, in determining whether
the Necessary and Proper Clause grants Congress the
legislative authority to enact a particular federal statute,
we look to see whether the statute constitutes a means
that is rationally related to the implementation of a con
stitutionally enumerated power. Sabri v. United States,
541 U. S. 600, 605 (2004) (using term “means-ends ration
ality” to describe the necessary relationship); ibid. (up
holding Congress’ “authority under the Necessary and
Proper Clause” to enact a criminal statute in furtherance
of the federal power granted by the Spending Clause); see
Gonzales v. Raich, 545 U. S. 1, 22 (2005) (holding that
because “Congress had a rational basis” for concluding
that a statute implements Commerce Clause power, the
statute falls within the scope of congressional “authority to
‘make all Laws which shall be necessary and proper’ to
‘regulate Commerce . . . among the several States’ ” (ellip
sis in original)); see also United States v. Lopez, 514 U. S.
549, 557 (1995); Hodel v. Virginia Surface Mining & Rec
lamation Assn., Inc., 452 U. S. 264, 276 (1981).
   Of course, as Chief Justice Marshall stated, a federal
                  Cite as: 560 U. S. ____ (2010)              7

                      Opinion of the Court

statute, in addition to being authorized by Art. I, §8, must
also “not [be] prohibited” by the Constitution. McCulloch,
supra, at 421. But as we have already stated, the present
statute’s validity under provisions of the Constitution
other than the Necessary and Proper Clause is an issue
that is not before us. Under the question presented, the
relevant inquiry is simply “whether the means chosen are
‘reasonably adapted’ to the attainment of a legitimate end
under the commerce power” or under other powers that
the Constitution grants Congress the authority to imple
ment. Gonzales, supra, at 37 (SCALIA, J., concurring in
judgment) (quoting United States v. Darby, 312 U. S. 100,
121 (1941)).
   We have also recognized that the Constitution “ad
dresse[s]” the “choice of means”
    “primarily . . . to the judgment of Congress. If it can
    be seen that the means adopted are really calculated
    to attain the end, the degree of their necessity, the ex
    tent to which they conduce to the end, the closeness of
    the relationship between the means adopted and the
    end to be attained, are matters for congressional de
    termination alone.” Burroughs v. United States, 290
    U. S. 534, 547–548 (1934).
See also Lottery Case, 188 U. S. 321, 355 (1903) (“[T]he
Constitution . . . . leaves to Congress a large discretion as
to the means that may be employed in executing a given
power”); Morrison, supra, at 607 (applying a “presumption
of constitutionality” when examining the scope of Con
gressional power); McCulloch, supra, at 410, 421.
   Thus, the Constitution, which nowhere speaks explicitly
about the creation of federal crimes beyond those related
to “counterfeiting,” “treason,” or “Piracies and Felonies
committed on the high Seas” or “against the Law of Na
tions,” Art. I, §8, cls. 6, 10; Art. III, §3, nonetheless grants
Congress broad authority to create such crimes. See
8               UNITED STATES v. COMSTOCK

                      Opinion of the Court

McCulloch, 4 Wheat., at 416 (“All admit that the govern
ment may, legitimately, punish any violation of its laws;
and yet, this is not among the enumerated powers of
Congress”); see also United States v. Fox, 95 U. S. 670, 672
(1878). And Congress routinely exercises its authority to
enact criminal laws in furtherance of, for example, its
enumerated powers to regulate interstate and foreign
commerce, to enforce civil rights, to spend funds for the
general welfare, to establish federal courts, to establish
post offices, to regulate bankruptcy, to regulate naturali
zation, and so forth. Art. I, §8, cls. 1, 3, 4, 7, 9; Amdts. 13–
15. See, e.g., Lottery Case, supra (upholding criminal
statute enacted in furtherance of the Commerce Clause);
Ex parte Yarbrough, 110 U. S. 651 (1884) (upholding
Congress’ authority to enact Rev. Stat. §5508, currently 18
U. S. C. §241 (criminalizing civil-rights violations) and
Rev. Stat. §5520, currently 42 U. S. C. §1973j (criminaliz
ing voting-rights violations) in furtherance of the Four
teenth and Fifteenth Amendments); Sabri, supra, (uphold
ing criminal statute enacted in furtherance of the
Spending Clause); Jinks, supra, at 462, n. 2 (citing
McCulloch, supra, at 417) (describing perjury and witness
tampering as federal crimes enacted in furtherance of the
power to constitute federal tribunals); see also 18 U. S. C.
§1691 et seq. (postal crimes); §151 et seq. (bankruptcy
crimes); 8 U. S. C. §§1324–1328 (immigration crimes).
   Similarly, Congress, in order to help ensure the en
forcement of federal criminal laws enacted in furtherance
of its enumerated powers, “can cause a prison to be erected
at any place within the jurisdiction of the United States,
and direct that all persons sentenced to imprisonment
under the laws of the United States shall be confined
there.” Ex parte Karstendick, 93 U. S. 396, 400 (1876).
Moreover, Congress, having established a prison system,
can enact laws that seek to ensure that system’s safe and
responsible administration by, for example, requiring
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                      Opinion of the Court

prisoners to receive medical care and educational training,
see, e.g., 18 U. S. C. §§4005–4006; §4042(a)(3), and can
also ensure the safety of the prisoners, prison workers and
visitors, and those in surrounding communities by, for
example, creating further criminal laws governing entry,
exit, and smuggling, and by employing prison guards to
ensure discipline and security. See, e.g., §1791 (prohibit
ing smuggling contraband); §751 et seq. (prohibiting es
cape and abetting thereof); 28 CFR §541.10 et seq. (2009)
(inmate discipline).
   Neither Congress’ power to criminalize conduct, nor its
power to imprison individuals who engage in that conduct,
nor its power to enact laws governing prisons and prison
ers, is explicitly mentioned in the Constitution. But Con
gress nonetheless possesses broad authority to do each of
those things in the course of “carrying into Execution” the
enumerated powers “vested by” the “Constitution in the
Government of the United States,” Art. I, §8, cl. 18—
authority granted by the Necessary and Proper Clause.
   Second, the civil-commitment statute before us consti
tutes a modest addition to a set of federal prison-related
mental-health statutes that have existed for many dec
ades. We recognize that even a longstanding history of
related federal action does not demonstrate a statute’s
constitutionality. See, e.g., Walz v. Tax Comm’n of City of
New York, 397 U. S. 664, 678 (1970) (“[N]o one acquires a
vested or protected right in violation of the Constitution by
long use . . .”); cf. Morrison, 529 U. S., at 612–614 (legisla
tive history is neither necessary nor sufficient with respect
to Art. I analysis). A history of involvement, however, can
nonetheless be “helpful in reviewing the substance of a
congressional statutory scheme,” Gonzales, 545 U. S., at
21; Walz, supra, at 678, and, in particular, the reason
ableness of the relation between the new statute and pre
existing federal interests.
   Here, Congress has long been involved in the delivery of
10              UNITED STATES v. COMSTOCK

                      Opinion of the Court

mental health care to federal prisoners, and has long
provided for their civil commitment. In 1855 it estab
lished Saint Elizabeth’s Hospital in the District of Colum
bia to provide treatment to “the insane of the army and
navy . . . and of the District of Columbia.” Act of Mar. 3,
1855, 10 Stat. 682; 39 Stat. 309. In 1857 it provided for
confinement at Saint Elizabeth’s of any person within the
District of Columbia who had been “charged with [a]
crime” and who was “insane” or later became “insane
during the continuance of his or her sentence in the
United States penitentiary.” Act of Feb. 7, 1857, §§5–6, 11
Stat. 158; see 17 Op. Atty. Gen. 211, 212–213 (1881). In
1874, expanding the geographic scope of its statutes,
Congress provided for civil commitment in federal facili
ties (or in state facilities if a State so agreed) of “all per
sons who have been or shall be convicted of any offense in
any court of the United States” and who are or “shall
become” insane “during the term of their imprisonment.”
Act of June 23, 1874, ch. 465, 18 Stat. 251 (emphasis
added). And in 1882 Congress provided for similar com
mitment of those “charged” with federal offenses who
become “insane” while in the “custody” of the United
States. Act of Aug. 7, 1882, 22 Stat. 330 (emphasis
added). Thus, over the span of three decades, Congress
created a national, federal civil-commitment program
under which any person who was either charged with or
convicted of any federal offense in any federal court could
be confined in a federal mental institution.
   These statutes did not raise the question presented
here, for they all provided that commitment in a federal
hospital would end upon the completion of the relevant
“terms” of federal “imprisonment” as set forth in the un
derlying criminal sentence or statute. §§2–3, 18 Stat. 252;
see 35 Op. Atty. Gen. 366, 368 (1927); cf. 30 Op. Atty. Gen.
569, 571 (1916). But in the mid-1940’s that proviso was
eliminated.
                 Cite as: 560 U. S. ____ (2010)          11

                     Opinion of the Court

  In 1945 the Judicial Conference of the United States
proposed legislative reforms of the federal civil
commitment system. The Judicial Conference based its
proposals upon what this Court has described as a “long
study by a conspicuously able committee” (chaired by
Judge Calvert Magruder and whose members included
Judge Learned Hand), involving consultation “with federal
district and circuit judges” across the country as well as
with the Department of Justice. Greenwood v. United
States, 350 U. S. 366, 373 (1956); Greenwood v. United
States, 219 F. 2d 376, 380–384 (CA8 1955) (describing the
committee’s work). The committee studied, among other
things, the “serious problem faced by the Bureau of Pris
ons, namely, what to do with insane criminals upon the
expiration of their terms of confinement, where it would be
dangerous to turn them loose upon society and where no
state will assume responsibility for their custody.” Judi
cial Conference, Report of Committee to Study Treatment
Accorded by Federal Courts to Insane Persons Charged
with Crime 11 (1945) (hereinafter Committee Report),
App. 73. The committee provided examples of instances in
which the Bureau of Prisons had struggled with the prob
lem of “ ‘paranoid’ ” and “ ‘threatening’ ” individuals whom
no State would accept. Id., at 9, App. 71. And it noted
that, in the Bureau’s “[e]xperience,” States would not
accept an “appreciable number” of “mental[ly] incompe
tent” individuals “nearing expiration” of their prison
terms, because of their “lack of legal residence in any
State,” even though those individuals “ought not . . . be at
large because they constitute a menace to public safety.”
H. R. Rep. No. 1319, 81st Cong., 1st Sess., 2 (1949) (state
ment of James V. Bennett, Director); see also Letter from
Bennett to Judge Magruder, attachment to Committee
Report, App. 83–88. The committee, hence the Judicial
Conference, therefore recommended that Congress enact
“some provision of law authorizing the continued confine
12               UNITED STATES v. COMSTOCK

                       Opinion of the Court

ment of such persons after their sentences expired.”
Committee Report 11, App. 73; see also Report of the
Judicial Conference of Senior Circuit Judges 13 (1945).
  Between 1948 and 1949, following its receipt of the
Judicial Conference report, Congress modified the law.
See Act of June 25, 1948, 62 Stat. 855, 18 U. S. C. §§4241–
4243 (1952 ed.); Act of Sept. 7, 1949, 63 Stat. 686, 18
U. S. C. §§4244–4248. It provided for the civil commit
ment of individuals who are, or who become, mentally
incompetent at any time after their arrest and before the
expiration of their federal sentence, §§4241, 4244, 4247–
4248; and it set forth various procedural safeguards,
§§4242, 4246, 4247. With respect to an individual whose
prison term is about to expire, it specified the following:
        “Whenever the Director of the Bureau of Prisons
     shall certify that a prisoner whose sentence is about to
     expire has been examined [and] . . . in the judgment of
     the Director and the board of examiners the prisoner
     is insane or mentally incompetent, and . . . if released
     he will probably endanger the safety of the officers,
     the property, or other interests of the United States,
     and that suitable arrangements for the custody and
     care of the prisoner are not otherwise available, the
     Attorney General shall transmit the certificate to . . .
     the court for the district in which the prisoner is con
     fined. Whereupon the court shall cause the prisoner
     to be examined . . . and shall . . . hold a hearing . . . . If
     upon such hearing the court shall determine that the
     conditions specified above exist, the court may commit
     the prisoner to the custody of the Attorney General or
     his authorized representative.” §4247.
The precondition that the mentally ill individual’s release
would “probably endanger the safety of the officers, the
property, or other interests of the United States” was
uniformly interpreted by the Judiciary to mean that his
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                     Opinion of the Court

“release would endanger the safety of persons, property or
the public interest in general—not merely the interests
peculiar to the United States as such.” United States v.
Curry, 410 F. 2d 1372, 1374 (CA4 1969); see also Royal v.
United States, 274 F. 2d 846, 851–852 (CA10 1960).
  In 1984, Congress modified these basic statutes. See
Insanity Defense Reform Act of 1984, 98 Stat. 2057, 18
U. S. C. §§4241–4247 (2006 ed.). As relevant here, it
altered the provision just discussed, regarding the pris
oner’s danger to the “interests of the United States,” to
conform more closely to the then-existing judicial interpre
tation of that language, i.e., it altered the language so as
to authorize (explicitly) civil commitment if, in addition to
the other conditions, the prisoner’s “release would create a
substantial risk of bodily injury to another person or
serious damage to the property of another.” §4246(d).
  Congress also elaborated upon the required condition
“that suitable arrangements . . . are not otherwise avail
able” by directing the Attorney General to seek alternative
placement in state facilities, as we have set forth above.
See ibid.; supra, at 2–3. With these modifications, the
statutes continue to authorize the civil commitment of
individuals who are both mentally ill and dangerous, once
they have been charged with, or convicted of, a federal
crime. §§4241(d), 4246; see also §4243(d). They continue
to provide for the continued civil commitment of those
individuals when they are “due for release” from federal
custody because their “sentence is about to expire.” §4246.
And, as we have previously set forth, they establish vari
ous procedural and other requirements. E.g., §4247.
  In 2006, Congress enacted the particular statute before
us. §302, 120 Stat. 619, 18 U. S. C. §4248. It differs from
earlier statutes in that it focuses directly upon persons
who, due to a mental illness, are sexually dangerous.
Notably, many of these individuals were likely already
subject to civil commitment under §4246, which, since
14             UNITED STATES v. COMSTOCK

                     Opinion of the Court

1949, has authorized the postsentence detention of federal
prisoners who suffer from a mental illness and who are
thereby dangerous (whether sexually or otherwise). But
cf. H. R. Rep. No. 109–218, pt. 1, p. 29 (2005). Aside from
its specific focus on sexually dangerous persons, §4248 is
similar to the provisions first enacted in 1949. Cf. §4246.
In that respect, it is a modest addition to a longstanding
federal statutory framework, which has been in place
since 1855.
   Third, Congress reasonably extended its longstanding
civil-commitment system to cover mentally ill and sexually
dangerous persons who are already in federal custody,
even if doing so detains them beyond the termination of
their criminal sentence. For one thing, the Federal Gov
ernment is the custodian of its prisoners. As federal cus
todian, it has the constitutional power to act in order to
protect nearby (and other) communities from the danger
federal prisoners may pose. Cf. Youngberg v. Romeo, 457
U. S. 307, 320 (1982) (“In operating an institution such as
[a prison system], there are occasions in which it is neces
sary for the State to restrain the movement of residents—
for example, to protect them as well as others from vio
lence” (emphasis added)). Indeed, at common law, one
“who takes charge of a third person” is “under a duty to
exercise reasonable care to control” that person to prevent
him from causing reasonably foreseeable “bodily harm to
others.”    Restatement (Second) of Torts §319, p. 129
(1963–1964); see Volungus, 595 F. 3d, at 7–8 (citing cases);
see also United States v. S. A., 129 F. 3d 995, 999 (CA8
1997) (“[Congress enacted §4246] to avert the public dan
ger likely to ensue from the release of mentally ill and
dangerous detainees”). If a federal prisoner is infected
with a communicable disease that threatens others, surely
it would be “necessary and proper” for the Federal Gov
ernment to take action, pursuant to its role as federal
custodian, to refuse (at least until the threat diminishes)
                 Cite as: 560 U. S. ____ (2010)           15

                     Opinion of the Court

to release that individual among the general public, where
he might infect others (even if not threatening an inter
state epidemic, cf. Art. I, §8, cl. 3). And if confinement of
such an individual is a “necessary and proper” thing to do,
then how could it not be similarly “necessary and proper”
to confine an individual whose mental illness threatens
others to the same degree?
   Moreover, §4248 is “reasonably adapted,” Darby, 312
U. S., at 121, to Congress’ power to act as a responsible
federal custodian (a power that rests, in turn, upon federal
criminal statutes that legitimately seek to implement
constitutionally enumerated authority, see supra, at 7–8).
Congress could have reasonably concluded that federal
inmates who suffer from a mental illness that causes them
to “have serious difficulty in refraining from sexually
violent conduct,” §4247(a)(6), would pose an especially
high danger to the public if released. Cf. H. R. Rep. No.
109–218, at 22–23. And Congress could also have rea
sonably concluded (as detailed in the Judicial Conference’s
report) that a reasonable number of such individuals
would likely not be detained by the States if released from
federal custody, in part because the Federal Government
itself severed their claim to “legal residence in any State”
by incarcerating them in remote federal prisons. H. R.
Rep. No. 1319, at 2; Committee Report 7–11, App. 69–75;
cf. post, at 6 (KENNEDY, J., concurring in judgment). Here
Congress’ desire to address the specific challenges identi
fied in the Reports cited above, taken together with its
responsibilities as a federal custodian, supports the con
clusion that §4248 satisfies “review for means-end ration
ality,” i.e., that it satisfies the Constitution’s insistence
that a federal statute represent a rational means for im
plementing a constitutional grant of legislative authority.
Sabri, 541 U. S., at 605 (citing McCulloch, 4 Wheat. 316).
See Jinks, 538 U. S., at 462–463 (opinion for the Court by
SCALIA, J.) (holding that a statute is authorized by the
16              UNITED STATES v. COMSTOCK

                      Opinion of the Court

Necessary and Proper Clause when it “provides an alter
native to [otherwise] unsatisfactory options” that are
“obviously inefficient”).
   Fourth, the statute properly accounts for state interests.
Respondents and the dissent contend that §4248 violates
the Tenth Amendment because it “invades the province of
state sovereignty” in an area typically left to state control.
New York v. United States, 505 U. S. 144, 155 (1992); see
Brief for Respondents 35–47; post, at 7–8, 19–23 (THOMAS,
J., dissenting). See also Jackson v. Indiana, 406 U. S. 715,
736 (1972) (“The States have traditionally exercised broad
power to commit persons found to be mentally ill”). But
the Tenth Amendment’s text is clear: “The powers not
delegated to the United States by the Constitution, nor
prohibited by it to the States, are reserved to the States
respectively, or to the people.” (Emphasis added.) The
powers “delegated to the United States by the Constitu
tion” include those specifically enumerated powers listed
in Article I along with the implementation authority
granted by the Necessary and Proper Clause. Virtually by
definition, these powers are not powers that the Constitu
tion “reserved to the States.” See New York, supra, at 156,
159 (“[I]f a power is delegated to Congress in the Constitu
tion, the Tenth Amendment expressly disclaims any res
ervation of that power to the States . . . .” “In the end . . .
it makes no difference whether one views the question at
issue in these cases as one of ascertaining the limits of the
power delegated to the Federal Government under the
affirmative provisions of the Constitution or one of dis
cerning the core of sovereignty retained by the States
under the Tenth Amendment”); Darby, supra, at 123–124;
see also Hodel, 452 U. S., at 276–277, 281; Maryland v.
Wirtz, 392 U. S. 183, 195–196 (1968); Lambert v. Yellow
ley, 272 U. S. 581, 596 (1926).
   Nor does this statute invade state sovereignty or other
wise improperly limit the scope of “powers that remain
                 Cite as: 560 U. S. ____ (2010)          17

                     Opinion of the Court

with the States.” Post, at 7 (THOMAS, J., dissenting). To
the contrary, it requires accommodation of state interests:
The Attorney General must inform the State in which the
federal prisoner “is domiciled or was tried” that he is
detaining someone with respect to whom those States may
wish to assert their authority, and he must encourage
those States to assume custody of the individual.
§4248(d). He must also immediately “release” that person
“to the appropriate official of” either State “if such State
will assume [such] responsibility.” Ibid. And either State
has the right, at any time, to assert its authority over the
individual, which will prompt the individual’s immediate
transfer to State custody. §4248(d)(1). Respondents con
tend that the States are nonetheless “powerless to prevent
the detention of their citizens under §4248, even if deten
tion is contrary to the States’ policy choices.” Brief for
Respondents 11 (emphasis added). But that is not the
most natural reading of the statute, see §§4248(d)(1)–(e),
and the Solicitor General acknowledges that “the Federal
Government would have no appropriate role” with respect
to an individual covered by the statute once “the transfer
to State responsibility and State control has occurred.” Tr.
of Oral Arg. 9.
   In Greenwood, 350 U. S. 366, the Court rejected a chal
lenge to the current statute’s predecessor—i.e., to the 1949
statute we described above, supra, at 11–12. The petition
ers in that case claimed, like the respondents here, that
the statute improperly interfered with state sovereignty.
See Brief for Petitioner in Greenwood v. United States,
O. T. 1955, No. 460, pp. 2, 18–29. But the Court rejected
that argument. See Greenwood, supra, at 375–376. And
the version of the statute at issue in Greenwood was less
protective of state interests than the current statute. That
statute authorized federal custody so long as “suitable
arrangements” were “not otherwise available” in a State or
otherwise. 63 Stat. 687 (emphasis added). Cf. Brief for
18              UNITED STATES v. COMSTOCK

                     Opinion of the Court

Petitioner in Greenwood, supra, at 25 (“What has really
happened is that the Federal government has been dissat
isfied with the care given by the states to those mentally
incompetent who have been released by the Federal au
thorities”). Here, by contrast, as we have explained, §4248
requires the Attorney General to encourage the relevant
States to take custody of the individual without inquiring
into the “suitability” of their intended care or treatment,
and to relinquish federal authority whenever a State
asserts its own. §4248(d). Thus, if the statute at issue in
Greenwood did not invade state interests, then, a fortiori,
neither does §4248.
   Fifth, the links between §4248 and an enumerated
Article I power are not too attenuated. Neither is the
statutory provision too sweeping in its scope. Invoking the
cautionary instruction that we may not “pile inference
upon inference” in order to sustain congressional action
under Article I, Lopez, 514 U. S., at 567, respondents
argue that, when legislating pursuant to the Necessary
and Proper Clause, Congress’ authority can be no more
than one step removed from a specifically enumerated
power. See Brief for Respondents 21–22; Tr. of Oral Arg.
27–28. But this argument is irreconcilable with our prece
dents. Again, take Greenwood as an example. In that
case we upheld the (likely indefinite) civil commitment of
a mentally incompetent federal defendant who was ac
cused of robbing a United States Post Office. 350 U. S., at
369, 375. The underlying enumerated Article I power was
the power to “Establish Post Offices and Post Roads.”
Art. I, §8, cl. 7. But, as Chief Justice Marshall recognized
in McCulloch,
     “the power ‘to establish post offices and post roads’
     . . . is executed by the single act of making the estab
     lishment. . . . [F]rom this has been inferred the power
     and duty of carrying the mail along the post road,
                 Cite as: 560 U. S. ____ (2010)          19

                     Opinion of the Court

    from one post office to another.          And, from
    this implied power, has again been inferred the right
    to punish those who steal letters from the post office,
    or rob the mail.” 4 Wheat., at 417 (emphasis added).
And, as we have explained, from the implied power to
punish we have further inferred both the power to im
prison, see supra, at 8–9, and, in Greenwood, the federal
civil-commitment power.
   Our necessary and proper jurisprudence contains multi
ple examples of similar reasoning. For example, in Sabri
we observed that “Congress has authority under the
Spending Clause to appropriate federal moneys” and that
it therefore “has corresponding authority under the Neces
sary and Proper Clause to see to it that taxpayer dollars”
are not “siphoned off” by “corrupt public officers.” 541
U. S., at 605 (citation omitted). We then further held that,
in aid of that implied power to criminalize graft of “tax
payer dollars,” Congress has the additional prophylactic
power to criminalize bribes or kickbacks even when the
stolen funds have not been “traceably skimmed from
specific federal payments.” Ibid. Similarly, in United
States v. Hall, 98 U. S. 343 (1879), we held that the Neces
sary and Proper Clause grants Congress the power, in
furtherance of Art. I, §8, cls. 11–13, to award “pensions to
the wounded and disabled” soldiers of the armed forces
and their dependents, 98 U. S. at 351; and from that im
plied power we further inferred the “[i]mplied power” “to
pass laws to . . . punish” anyone who fraudulently appro
priated such pensions, id., at 346. See also Stewart v.
Kahn, 11 Wall. 493, 506–507 (1871).
   Indeed even the dissent acknowledges that Congress
has the implied power to criminalize any conduct that
might interfere with the exercise of an enumerated power,
and also the additional power to imprison people who
violate those (inferentially authorized) laws, and the
20              UNITED STATES v. COMSTOCK

                      Opinion of the Court

additional power to provide for the safe and reasonable
management of those prisons, and the additional power to
regulate the prisoners’ behavior even after their release.
See post, at 12–13, 17, n. 11. Of course, each of those
powers, like the powers addressed in Sabri, Hall, and
McCulloch, is ultimately “derived from” an enumerated
power, Hall, supra, at 345. And, as the dissent agrees,
that enumerated power is “the enumerated power that
justifies the defendant’s statute of conviction,” post, at 17,
n. 11. Neither we nor the dissent can point to a single
specific enumerated power “that justifies a criminal de
fendant’s arrest or conviction,” post, at 12, in all cases
because Congress relies on different enumerated powers
(often, but not exclusively, its Commerce Clause power) to
enact its various federal criminal statutes, see supra, at 7–
8. But every such statute must itself be legitimately
predicated on an enumerated power. And the same enu
merated power that justifies the creation of a federal
criminal statute, and that justifies the additional implied
federal powers that the dissent considers legitimate, justi
fies civil commitment under §4248 as well. See supra, at
14–16. Thus, we must reject respondents’ argument that
the Necessary and Proper Clause permits no more than a
single step between an enumerated power and an Act of
Congress.
   Nor need we fear that our holding today confers on
Congress a general “police power, which the Founders
denied the National Government and reposed in the
States.” Morrison, 529 U. S., at 618. As the Solicitor
General repeatedly confirmed at oral argument, §4248 is
narrow in scope. It has been applied to only a small frac
tion of federal prisoners. See Tr. of Oral Arg. 24–25 (105
individuals have been subject to §4248 out of over 188,000
federal inmates); see also Dept. of Justice, Bureau of
Justice Statistics, W. Sabol, H. West, & M. Cooper, Pris
oners in 2008, p. 8 (rev. Apr. 2010) (Table 8), online at
                 Cite as: 560 U. S. ____ (2010)           21

                     Opinion of the Court

http://bjs.ojp.usdoj.gov/content/pub/pdf/p08.pdf/ (as visited
May 4, 2010, and available in Clerk of Court’s case file).
And its reach is limited to individuals already “in the
custody of the” Federal Government. §4248(a); Tr. of Oral
Arg. 7 (“[Federal authority for §4248] has always de
pended on the fact of Federal custody, on the fact that this
person has entered the criminal justice system . . .”).
Indeed, the Solicitor General argues that “the Federal
Government would not have . . . the power to commit a
person who . . . has been released from prison and whose
period of supervised release is also completed.” Id., at 9.
Thus, far from a “general police power,” §4248 is a rea
sonably adapted and narrowly tailored means of pursuing
the Government’s legitimate interest as a federal custo
dian in the responsible administration of its prison
system.
  To be sure, as we have previously acknowledged,
    “The Federal Government undertakes activities today
    that would have been unimaginable to the Framers in
    two senses; first, because the Framers would not have
    conceived that any government would conduct such
    activities; and second, because the Framers would not
    have believed that the Federal Government, rather
    than the States, would assume such responsibilities.
    Yet the powers conferred upon the Federal Govern
    ment by the Constitution were phrased in language
    broad enough to allow for the expansion of the Federal
    Government’s role.” New York, 505 U. S., at 157.
The Framers demonstrated considerable foresight in
drafting a Constitution capable of such resilience through
time. As Chief Justice Marshall observed nearly 200 years
ago, the Necessary and Proper Clause is part of “a consti
tution intended to endure for ages to come, and, conse
quently, to be adapted to the various crises of human
affairs.” McCulloch, 4 Wheat., at 415 (emphasis deleted).
22              UNITED STATES v. COMSTOCK

                      Opinion of the Court

                         *    *     *
   We take these five considerations together. They in
clude: (1) the breadth of the Necessary and Proper Clause,
(2) the long history of federal involvement in this arena,
(3) the sound reasons for the statute’s enactment in light
of the Government’s custodial interest in safeguarding the
public from dangers posed by those in federal custody, (4)
the statute’s accommodation of state interests, and (5) the
statute’s narrow scope. Taken together, these considera
tions lead us to conclude that the statute is a “necessary
and proper” means of exercising the federal authority that
permits Congress to create federal criminal laws, to pun
ish their violation, to imprison violators, to provide appro
priately for those imprisoned, and to maintain the security
of those who are not imprisoned but who may be affected
by the federal imprisonment of others. The Constitution
consequently authorizes Congress to enact the statute.
   We do not reach or decide any claim that the statute or
its application denies equal protection of the laws, proce
dural or substantive due process, or any other rights
guaranteed by the Constitution. Respondents are free to
pursue those claims on remand, and any others they have
preserved.
   The judgment of the Court of Appeals for the Fourth
Circuit with respect to Congress’ power to enact this stat
ute is reversed, and the case is remanded for further
proceedings consistent with this opinion.
                                              It is so ordered.
                 Cite as: 560 U. S. ____ (2010)           1

              KENNEDY, J., concurring in judgment

SUPREME COURT OF THE UNITED STATES
                         _________________

                         No. 08–1224
                         _________________


     UNITED STATES, PETITIONER v. GRAYDON 

           EARL COMSTOCK, JR., ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FOURTH CIRCUIT

                        [May 17, 2010] 


  JUSTICE KENNEDY, concurring in the judgment.
   The Court is correct, in my view, to hold that the chal
lenged portions of 18 U. S. C. §4248 are necessary and
proper exercises of congressional authority.
   Respondents argue that congressional authority under
the Necessary and Proper Clause can be no more than one
step removed from an enumerated power. This is incor
rect. When the inquiry is whether a federal law has suffi
cient links to an enumerated power to be within the scope
of federal authority, the analysis depends not on the num
ber of links in the congressional-power chain but on the
strength of the chain.
   Concluding that a relation can be put into a verbal
formulation that fits somewhere along a causal chain of
federal powers is merely the beginning, not the end, of the
constitutional inquiry. See United States v. Lopez, 514
U. S. 549, 566–567 (1995). The inferences must be con
trolled by some limitations lest, as Thomas Jefferson
warned, congressional powers become completely un
bounded by linking one power to another ad infinitum in a
veritable game of “ ‘this is the house that Jack built.’ ”
Letter from Thomas Jefferson to Edward Livingston (Apr.
30, 1800), 31 The Papers of Thomas Jefferson 547 (B.
Oberg ed. 2004); see also United States v. Patton, 451
F. 3d 615, 628 (CA10 2006).
2               UNITED STATES v. COMSTOCK

               KENNEDY, J., concurring in judgment

   This separate writing serves two purposes. The first is
to withhold assent from certain statements and proposi
tions of the Court’s opinion. The second is to caution that
the Constitution does require the invalidation of congres
sional attempts to extend federal powers in some
instances.
                               I
   The Court concludes that, when determining whether
Congress has the authority to enact a specific law under
the Necessary and Proper Clause, we look “to see whether
the statute constitutes a means that is rationally related
to the implementation of a constitutionally enumerated
power.” Ante, at 6 (suggesting that Sabri v. United States,
541 U. S. 600, 605 (2004), adopts a “means-ends rational
ity” test).
   The terms “rationally related” and “rational basis” must
be employed with care, particularly if either is to be used
as a stand-alone test. The phrase “rational basis” most
often is employed to describe the standard for determining
whether legislation that does not proscribe fundamental
liberties nonetheless violates the Due Process Clause.
Referring to this due process inquiry, and in what must be
one of the most deferential formulations of the standard
for reviewing legislation in all the Court’s precedents, the
Court has said: “But the law need not be in every respect
logically consistent with its aims to be constitutional. It is
enough that there is an evil at hand for correction, and
that it might be thought that the particular legislative
measure was a rational way to correct it.” Williamson v.
Lee Optical of Okla., Inc., 348 U. S. 483, 487–488 (1955).
This formulation was in a case presenting a due process
challenge and a challenge to a State’s exercise of its own
powers, powers not confined by the principles that control
the limited nature of our National Government. The
phrase, then, should not be extended uncritically to the
                  Cite as: 560 U. S. ____ (2010)            3

               KENNEDY, J., concurring in judgment

issue before us.
    The operative constitutional provision in this case is the
Necessary and Proper Clause. This Court has not held
that the Lee Optical test, asking if “it might be thought
that the particular legislative measure was a rational way
to correct” an evil, is the proper test in this context.
Rather, under the Necessary and Proper Clause, applica
tion of a “rational basis” test should be at least as exacting
as it has been in the Commerce Clause cases, if not more
so. Indeed, the cases the Court cites in the portion of its
opinion referring to “rational basis” are predominantly
Commerce Clause cases, and none are due process cases.
See ante, at 6 (citing Gonzales v. Raich, 545 U. S. 1 (2005);
Lopez, supra; Hodel v. Virginia Surface Mining & Recla
mation Assn., Inc., 452 U. S. 264, 276 (1981)).
    There is an important difference between the two ques
tions, but the Court does not make this distinction clear.
Raich, Lopez, and Hodel were all Commerce Clause cases.
Those precedents require a tangible link to commerce, not
a mere conceivable rational relation, as in Lee Optical.
“ ‘[S]imply because Congress may conclude that a particu
lar activity substantially affects interstate commerce does
not necessarily make it so.’ ” Lopez, supra, at 557, n. 2
(quoting Hodel, supra, at 311 (Rehnquist, J., concurring in
judgment)). The rational basis referred to in the Com
merce Clause context is a demonstrated link in fact, based
on empirical demonstration. While undoubtedly deferen
tial, this may well be different from the rational-basis test
as Lee Optical described it.
    The Court relies on Sabri, supra, for its conclusion that
a “means-ends rationality” is all that is required for a
power to come within the Necessary and Proper Clause’s
reach. See ante, at 6. Sabri only refers to “means-ends
rationality” in a parenthetical describing the holding in
McCulloch v. Maryland, 4 Wheat. 316 (1819); it certainly
did not import the Lee Optical rational-basis test into this
4              UNITED STATES v. COMSTOCK

              KENNEDY, J., concurring in judgment

arena through such a parenthetical. See Sabri, supra, at
612 (THOMAS, J., concurring in judgment) (“A statute can
have a ‘rational’ connection to an enumerated power with
out being obviously or clearly tied to that enumerated
power”). It should be remembered, moreover, that the
spending power is not designated as such in the Constitu
tion but rather is implied from the power to lay and collect
taxes and other specified exactions in order, among other
purposes, “to pay the Debts and provide for the common
Defence and general Welfare of the United States.” Art. I,
§8, cl. 1; see South Dakota v. Dole, 483 U. S. 203, 206
(1987). The limits upon the spending power have not been
much discussed, but if the relevant standard is parallel to
the Commerce Clause cases, then the limits and the ana
lytic approach in those precedents should be respected.
   A separate concern stems from the Court’s explanation
of the Tenth Amendment. Ante, at 16. I had thought it a
basic principle that the powers reserved to the States
consist of the whole, undefined residuum of power remain
ing after taking account of powers granted to the National
Government. The Constitution delegates limited powers
to the National Government and then reserves the re
mainder for the States (or the people), not the other way
around, as the Court’s analysis suggests. And the powers
reserved to the States are so broad that they remain unde
fined. Residual power, sometimes referred to (perhaps
imperfectly) as the police power, belongs to the States and
the States alone.
   It is correct in one sense to say that if the National
Government has the power to act under the Necessary and
Proper Clause then that power is not one reserved to the
States. But the precepts of federalism embodied in the
Constitution inform which powers are properly exercised
by the National Government in the first place. See Lopez,
514 U. S., at 580–581 (KENNEDY, J., concurring); see also
McCulloch, supra, at 421 (powers “consist[ent] with the
                  Cite as: 560 U. S. ____ (2010)             5

               KENNEDY, J., concurring in judgment

letter and spirit of the constitution, are constitutional”). It
is of fundamental importance to consider whether essen
tial attributes of state sovereignty are compromised by the
assertion of federal power under the Necessary and Proper
Clause; if so, that is a factor suggesting that the power is
not one properly within the reach of federal power.
   The opinion of the Court should not be interpreted to
hold that the only, or even the principal, constraints on
the exercise of congressional power are the Constitution’s
express prohibitions. The Court’s discussion of the Tenth
Amendment invites the inference that restrictions flowing
from the federal system are of no import when defining
the limits of the National Government’s power, as it pro
ceeds by first asking whether the power is within the
National Government’s reach, and if so it discards federal
ism concerns entirely.
   These remarks explain why the Court ignores important
limitations stemming from federalism principles. Those
principles are essential to an understanding of the func
tion and province of the States in our constitutional
structure.
                              II
   As stated at the outset, in this case Congress has acted
within its powers to ensure that an abrupt end to the
federal detention of prisoners does not endanger third
parties. Federal prisoners often lack a single home State
to take charge of them due to their lengthy prison stays, so
it is incumbent on the National Government to act. This
obligation, parallel in some respects to duties defined in
tort law, is not to put in motion a particular force (here an
unstable and dangerous person) that endangers others.
Having acted within its constitutional authority to detain
the person, the National Government can acknowledge a
duty to ensure that an abrupt end to the detention does
not prejudice the States and their citizens.
6              UNITED STATES v. COMSTOCK

              KENNEDY, J., concurring in judgment

   I would note, as the Court’s opinion does, that §4248
does not supersede the right and responsibility of the
States to identify persons who ought to be subject to civil
confinement. The federal program in question applies
only to those in federal custody and thus involves little
intrusion upon the ordinary processes and powers of the
States.
   This is not a case in which the National Government
demands that a State use its own governmental system to
implement federal commands. See Printz v. United States,
521 U. S. 898 (1997). It is not a case in which the Na
tional Government relieves the States of their own pri
mary responsibility to enact laws and policies for the
safety and well being of their citizens. See United States
v. Morrison, 529 U. S. 598 (2000). Nor is it a case in which
the exercise of national power intrudes upon functions and
duties traditionally committed to the State. See Lopez,
supra, at 580–581 (KENNEDY, J., concurring).
   Rather, this is a discrete and narrow exercise of author
ity over a small class of persons already subject to the
federal power. Importantly, §4248(d) requires the Attor
ney General to release any civil detainee “to the appropri
ate official of the State in which the person is domiciled or
was tried if such State will assume responsibility for his
custody, care, and treatment,” providing a strong assur
ance that the proffered reason for the legislation’s neces
sity is not a mere artifice.
   With these observations, I concur in the judgment of the
Court.
                 Cite as: 560 U. S. ____ (2010)            1

                ALITO, J., concurring in judgment

SUPREME COURT OF THE UNITED STATES
                          _________________

                          No. 08–1224
                          _________________


     UNITED STATES, PETITIONER v. GRAYDON 

           EARL COMSTOCK, JR., ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FOURTH CIRCUIT

                         [May 17, 2010] 


   JUSTICE ALITO, concurring in the judgment.
   I am concerned about the breadth of the Court’s lan
guage, see ante, at 2–4 (KENNEDY, J., concurring in judg
ment), and the ambiguity of the standard that the Court
applies, see post, at 9 (THOMAS, J., dissenting), but I am
persuaded, on narrow grounds, that it was “necessary and
proper” for Congress to enact the statute at issue in this
case, 18 U. S. C. §4248, in order to “carr[y] into Execution”
powers specifically conferred on Congress by the Constitu
tion, see Art. I, §8, cl. 18.
   Section 4248 was enacted to protect the public from
federal prisoners who suffer from “a serious mental ill
ness, abnormality, or disorder” and who, if released, would
have “serious difficulty in refraining from sexually violent
conduct or child molestation.”        See §§4247(a)(5), (6),
4248(d). Under this law, if neither the State of a pris
oner’s domicile nor the State in which the prisoner was
tried will assume the responsibility for the prisoner’s
“custody, care, and treatment,” the Federal Government is
authorized to undertake that responsibility. §4248(d).
The statute recognizes that, in many cases, no State will
assume the heavy financial burden of civilly committing a
dangerous federal prisoner who, as a result of lengthy
federal incarceration, no longer has any substantial ties to
any State.
2                   UNITED STATES v. COMSTOCK

                    ALITO, J., concurring in judgment

  I entirely agree with the dissent that “[t]he Necessary
and Proper Clause empowers Congress to enact only those
laws that ‘carr[y] into Execution’ one or more of the federal
powers enumerated in the Constitution,” post, at 1, but
§4248 satisfies that requirement because it is a necessary
and proper means of carrying into execution the enumer
ated powers that support the federal criminal statutes
under which the affected prisoners were convicted. The
Necessary and Proper Clause provides the constitutional
authority for most federal criminal statutes. In other
words, most federal criminal statutes rest upon a congres
sional judgment that, in order to execute one or more of
the powers conferred on Congress, it is necessary and
proper to criminalize certain conduct, and in order to do
that it is obviously necessary and proper to provide for the
operation of a federal criminal justice system and a federal
prison system.
  All of this has been recognized since the beginning of
our country. The First Congress enacted federal criminal
laws,1 created federal law enforcement and prosecutorial
positions,2 established a federal court system,3 provided
for the imprisonment of persons convicted of federal
crimes,4 and gave United States marshals the responsibil
——————
    1 See, e.g., ch. 9, 1 Stat. 112 (“An Act for the Punishment of certain
Crimes against the United States”).
   2 Ch. 20, §35, id., at 92 (“[T]here shall be appointed in each district a

meet person learned in the law to act as attorney for the United States
in such district, . . . whose duty it shall be to prosecute in such district
all delinquents for crimes and offences, cognizable under the authority
of the United States”).
   3 §1, id., at 73 (“An Act to establish the Judicial Courts of the United

States”).
   4 See, e.g., §9, id., at 76–77 (providing that the federal district courts

shall have exclusive jurisdiction over “all crimes and offences that shall
be cognizable under the authority of the United States, . . . where no
other punishment than whipping, not exceeding thirty stripes, a fine
not exceeding one hundred dollars, or a term of imprisonment not
                      Cite as: 560 U. S. ____ (2010)                       3

                    ALITO, J., concurring in judgment

ity of securing federal prisoners.5
   The only additional question presented here is whether,
in order to carry into execution the enumerated powers on
which the federal criminal laws rest, it is also necessary
and proper for Congress to protect the public from dangers
created by the federal criminal justice and prison systems.
In my view, the answer to that question is “yes.” Just as it
is necessary and proper for Congress to provide for the
apprehension of escaped federal prisoners, it is necessary
and proper for Congress to provide for the civil commit
ment of dangerous federal prisoners who would otherwise
escape civil commitment as a result of federal imprison
ment.
   Some years ago, a distinguished study group created by
the Judicial Conference of the United States found that, in
a disturbing number of cases, no State was willing to
assume the financial burden of providing for the civil
commitment of federal prisoners who, if left at large after
the completion of their sentences, would present a danger
to any communities in which they chose to live or visit.
See ante, at 11; Greenwood v. United States, 350 U. S. 366,
373–374 (1956). These federal prisoners, having been held

——————
exceeding six months, is to be inflicted”); see also J. Roberts, The
Federal Bureau of Prisons: Its Mission, Its History, and Its Partnership
With Probation and Pretrial Services, 61 Fed. Probation 53 (1997)
(explaining that federal prisoners were originally housed in state and
county facilities on a contract basis).
  5 See ch. 20, §27, 1 Stat. 87 (“[A] marshal shall be appointed in and

for each district for the term of four years, . . . whose duty it shall be to
attend the district and circuit courts when sitting therein, . . . [a]nd to
execute throughout the district, all lawful precepts directed to him, and
issued under the authority of the United States”); id., at 88 (“[T]he
marshal shall be held answerable for the delivery to his successor of all
prisoners which may be in his custody at the time of his removal, or
when the term for which he is appointed shall expire, and for that
purpose may retain such prisoners in his custody until his successor
shall be appointed and qualified as the law directs”).
4              UNITED STATES v. COMSTOCK

                ALITO, J., concurring in judgment

for years in a federal prison, often had few ties to any
State; it was a matter of speculation where they would
choose to go upon release; and accordingly no State was
enthusiastic about volunteering to shoulder the burden of
civil commitment.
  The Necessary and Proper Clause does not give Con
gress carte blanche. Although the term “necessary” does
not mean “absolutely necessary” or indispensable, the
term requires an “appropriate” link between a power
conferred by the Constitution and the law enacted by
Congress. See McCulloch v. Maryland, 4 Wheat. 316, 415
(1819). And it is an obligation of this Court to enforce
compliance with that limitation. Id., at 423.
  The law in question here satisfies that requirement.
This is not a case in which it is merely possible for a court
to think of a rational basis on which Congress might have
perceived an attenuated link between the powers underly
ing the federal criminal statutes and the challenged civil
commitment provision. Here, there is a substantial link to
Congress’ constitutional powers.
  For this reason, I concur in the judgment that Congress
had the constitutional authority to enact 18 U. S. C.
§4248.
                 Cite as: 560 U. S. ____ (2010)           1

                    THOMAS, J., dissenting

SUPREME COURT OF THE UNITED STATES
                         _________________

                         No. 08–1224
                         _________________


     UNITED STATES, PETITIONER v. GRAYDON 

           EARL COMSTOCK, JR., ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FOURTH CIRCUIT

                        [May 17, 2010] 


  JUSTICE THOMAS, with whom JUSTICE SCALIA joins in
all but Part III–A–1–b, dissenting.
  The Court holds today that Congress has power under
the Necessary and Proper Clause to enact a law authoriz
ing the Federal Government to civilly commit “sexually
dangerous person[s]” beyond the date it lawfully could
hold them on a charge or conviction for a federal crime. 18
U. S. C. §4248(a). I disagree. The Necessary and Proper
Clause empowers Congress to enact only those laws that
“carr[y] into Execution” one or more of the federal powers
enumerated in the Constitution. Art. I, §8, cl. 18. Because
§4248 “Execut[es]” no enumerated power, I must respect
fully dissent.
                             I
   “As every schoolchild learns, our Constitution estab
lishes a system of dual sovereignty between the States and
the Federal Government.” Gregory v. Ashcroft, 501 U. S.
452, 457 (1991). In our system, the Federal Government’s
powers are enumerated, and hence limited. See, e.g.,
McCulloch v. Maryland, 4 Wheat. 316, 405 (1819) (“This
government is acknowledged by all to be one of enumer
ated powers”). Thus, Congress has no power to act unless
the Constitution authorizes it to do so. United States v.
Morrison, 529 U. S. 598, 607 (2000) (“Every law enacted
2                 UNITED STATES v. COMSTOCK

                        THOMAS, J., dissenting

by Congress must be based on one or more of its powers
enumerated in the Constitution”). The States, in turn, are
free to exercise all powers that the Constitution does not
withhold from them. Amdt. 10 (“The powers not delegated
to the United States by the Constitution, nor prohibited by
it to the States, are reserved to the States respectively, or
to the people”).1 This constitutional structure establishes
different default rules for Congress and the States: Con
gress’ powers are “few and defined,” while those that
belong to the States “remain . . . numerous and indefinite.”
The Federalist No. 45, p. 328 (B. Wright ed. 1961) (J.
Madison).
   The Constitution plainly sets forth the “few and defined”
powers that Congress may exercise. Article I “vest[s]” in
Congress “[a]ll legislative Powers herein granted,” §1, and
carefully enumerates those powers in §8. The final clause
of §8, the Necessary and Proper Clause, authorizes Con
gress “[t]o make all Laws which shall be necessary and
proper for carrying into Execution the foregoing Powers,
and all other Powers vested by this Constitution in the
Government of the United States, or in any Department or
Officer thereof.” Art. I, §8, cl. 18. As the Clause’s place
ment at the end of §8 indicates, the “foregoing Powers” are
those granted to Congress in the preceding clauses of that
section. The “other Powers” to which the Clause refers are
those “vested” in Congress and the other branches by
other specific provisions of the Constitution.
   Chief Justice Marshall famously summarized Congress’
authority under the Necessary and Proper Clause in
McCulloch, which has stood for nearly 200 years as this
——————
  1 “With this careful last phrase, the [Tenth] Amendment avoids tak

ing any position on the division of power between the state govern
ments and the people of the States: It is up to the people of each State
to determine which ‘reserved’ powers their state government may
exercise.” U. S. Term Limits, Inc. v. Thornton, 514 U. S. 779, 848
(1995) (THOMAS, J., dissenting).
                  Cite as: 560 U. S. ____ (2010)            3

                     THOMAS, J., dissenting

Court’s definitive interpretation of that text:
    “Let the end be legitimate, let it be within the scope of
    the constitution, and all means which are appropriate,
    which are plainly adapted to that end, which are not
    prohibited, but consist with the letter and spirit of the
    constitution, are constitutional.” 4 Wheat., at 421.
   McCulloch’s summation is descriptive of the Clause
itself, providing that federal legislation is a valid exercise
of Congress’ authority under the Clause if it satisfies a
two-part test: First, the law must be directed toward a
“legitimate” end, which McCulloch defines as one “within
the scope of the [C]onstitution”—that is, the powers ex
pressly delegated to the Federal Government by some
provision in the Constitution. Second, there must be a
necessary and proper fit between the “means” (the federal
law) and the “end” (the enumerated power or powers) it is
designed to serve. Ibid. McCulloch accords Congress a
certain amount of discretion in assessing means-end fit
under this second inquiry. The means Congress selects
will be deemed “necessary” if they are “appropriate” and
“plainly adapted” to the exercise of an enumerated power,
and “proper” if they are not otherwise “prohibited” by the
Constitution and not “[in]consistent” with its “letter and
spirit.” Ibid.
   Critically, however, McCulloch underscores the linear
relationship the Clause establishes between the two in
quiries: Unless the end itself is “legitimate,” the fit be
tween means and end is irrelevant. In other words, no
matter how “necessary” or “proper” an Act of Congress
may be to its objective, Congress lacks authority to legis
late if the objective is anything other than “carrying into
Execution” one or more of the Federal Government’s enu
merated powers. Art. I, §8, cl. 18.
   This limitation was of utmost importance to the Fram
ers.     During the State ratification debates, Anti
4                 UNITED STATES v. COMSTOCK

                        THOMAS, J., dissenting

Federalists expressed concern that the Necessary and
Proper Clause would give Congress virtually unlimited
power. See, e.g., Essays of Brutus, in 2 The Complete
Anti-Federalist 421 (H. Storing ed. 1981). Federalist
supporters of the Constitution swiftly refuted that charge,
explaining that the Clause did not grant Congress any
freestanding authority, but instead made explicit what
was already implicit in the grant of each enumerated
power. Referring to the “powers declared in the Constitu
tion,” Alexander Hamilton noted that “it is expressly to
execute these powers that the sweeping clause . . . author
izes the national legislature to pass all necessary and
proper laws.” The Federalist No. 33, at 245. James Madi
son echoed this view, stating that “the sweeping clause . . .
only extend[s] to the enumerated powers.” 3 J. Elliot, The
Debates in the Several State Conventions on the Adoption
of the Federal Constitution 455 (2d ed. 1854) (hereinafter
Elliot). Statements by delegates to the state ratification
conventions indicate that this understanding was widely
held by the founding generation. E.g., id., at 245–246
(statement of George Nicholas) (“Suppose [the Necessary
and Proper Clause] had been inserted, at the end of every
power, that they should have power to make laws to carry
that power into execution; would that have increased their
powers? If, therefore, it could not have increased their
powers, if placed at the end of each power, it cannot in
crease them at the end of all”).2
——————
  2 See also 4 Elliot 141 (2d ed. 1836) (statement of William Maclaine)

(“This clause specifies that [Congress] shall make laws to carry into
execution all the powers vested by this Constitution, consequently they
can make no laws to execute any other power”); 2 id., at 468 (statement
of James Wilson) (“[W]hen it is said that Congress shall have power to
make all laws which shall be necessary and proper, those words are
limited and defined by the following, ‘for carrying into execution the
foregoing powers.’ [The Clause] is saying no more than that the powers
we have already particularly given, shall be effectually carried into
execution”); Barnett, The Original Meaning of the Necessary and
                    Cite as: 560 U. S. ____ (2010)                 5

                       THOMAS, J., dissenting

   Roughly 30 years after the Constitution’s ratification,
McCulloch firmly established this understanding in our
constitutional jurisprudence. 4 Wheat., at 421, 423. Since
then, our precedents uniformly have maintained that the
Necessary and Proper Clause is not an independent fount
of congressional authority, but rather “a caveat that Con
gress possesses all the means necessary to carry out the
specifically granted ‘foregoing’ powers of §8 ‘and all other
Powers vested by this Constitution.’ ” Kinsella v. United
States ex rel. Singleton, 361 U. S. 234, 247 (1960); Carter
v. Carter Coal Co., 298 U. S. 238, 291 (1936); see Alden v.
Maine, 527 U. S. 706, 739 (1999); Martin v. Hunter’s Les
see, 1 Wheat. 304, 326 (1816); see also Gonzales v. Raich,
545 U. S. 1, 39 (2005) (SCALIA, J., concurring in judgment)
(stating that, although the Clause “empowers Congress to
enact laws . . . that are not within its authority to enact in
isolation,” those laws must be “in effectuation of [Con
gress’] enumerated powers” (citing McCulloch, supra, at
421–422)).
                            II
  Section 4248 establishes a federal civil-commitment
regime for certain persons in the custody of the Federal
Bureau of Prisons (BOP).3 If the Attorney General dem
onstrates to a federal court by clear and convincing evi
dence that a person subject to the statute is “sexually
—————— 

Proper Clause, 6 U. Pa. J. Const. L. 183, 185–186 (2003); Lawson & 

Granger, The “Proper” Scope of Federal Power: A Jurisdictional Inter
pretation of the Sweeping Clause, 43 Duke L. J. 267, 274–275, and

n. 24 (1993).
   3 The statute authorizes the Attorney General to petition a federal

court to order the commitment of a person in BOP custody (1) who has
been convicted of a federal crime and is serving a federal prison sen
tence therefor, (2) who has been found mentally incompetent to stand
trial, or (3) “against whom all federal criminal charges have been
dismissed solely for reasons related to his mental condition.” 18
U. S. C. §4248(a).
6                 UNITED STATES v. COMSTOCK

                        THOMAS, J., dissenting

dangerous,”4 a court may order the person committed until
he is no longer a risk “to others,” even if that does not
occur until after his federal criminal sentence has expired
or the statute of limitations on the federal charge against
him has run. §§4248(a), (d)–(e).
  No enumerated power in Article I, §8, expressly dele
gates to Congress the power to enact a civil-commitment
regime for sexually dangerous persons, nor does any other
provision in the Constitution vest Congress or the other
branches of the Federal Government with such a power.
Accordingly, §4248 can be a valid exercise of congressional
authority only if it is “necessary and proper for carrying
into Execution” one or more of those federal powers actu
ally enumerated in the Constitution.
  Section 4248 does not fall within any of those powers.
The Government identifies no specific enumerated power
or powers as a constitutional predicate for §4248, and none
are readily discernable. Indeed, not even the Commerce
Clause—the enumerated power this Court has interpreted
most expansively, see, e.g., NLRB v. Jones & Laughlin
Steel Corp., 301 U. S. 1, 37 (1937)—can justify federal civil
detention of sex offenders. Under the Court’s precedents,
Congress may not regulate noneconomic activity (such as
sexual violence) based solely on the effect such activity
may have, in individual cases or in the aggregate, on
interstate commerce. Morrison, 529 U. S., at 617–618;
United States v. Lopez, 514 U. S. 549, 563–567 (1995).
That limitation forecloses any claim that §4248 carries
into execution Congress’ Commerce Clause power, and the
——————
   4 The Act defines a “sexually dangerous person” as one “who has en

gaged or attempted to engage in sexually violent conduct or child
molestation,” and “who is sexually dangerous to others.” §4247(a)(5).
It further defines “sexually dangerous to others” to mean a person who
“suffers from a serious mental illness” such that he would “have serious
difficulty in refraining from sexually violent conduct or child molesta
tion if released.” §4247(a)(6).
                    Cite as: 560 U. S. ____ (2010)                   7

                        THOMAS, J., dissenting

Government has never argued otherwise, see Tr. of Oral
Arg. 21–22.5
  This Court, moreover, consistently has recognized that
the power to care for the mentally ill and, where neces
sary, the power “to protect the community from the dan
gerous tendencies of some” mentally ill persons, are
among the numerous powers that remain with the States.
Addington v. Texas, 441 U. S. 418, 426 (1979). As a conse
quence, we have held that States may “take measures to
restrict the freedom of the dangerously mentally ill”—
including those who are sexually dangerous—provided
that such commitments satisfy due process and other
constitutional requirements. Kansas v. Hendricks, 521
U. S. 346, 363 (1997).
  Section 4248 closely resembles the involuntary civil
commitment laws that States have enacted under their
parens patriae and general police powers. Indeed, it is
clear, on the face of the Act and in the Government’s
arguments urging its constitutionality, that §4248 is
aimed at protecting society from acts of sexual violence,
not toward “carrying into Execution” any enumerated
power or powers of the Federal Government. See Adam
Walsh Child Protection and Safety Act of 2006, 120 Stat.
587 (entitled “[a]n Act [t]o protect children from sexual
exploitation and violent crime”), §102, id., at 590 (state
ment of purpose declaring that the Act was promulgated
“to protect the public from sex offenders”); Brief for United
States 38–39 (asserting the Federal Government’s power
to “protect the public from harm that might result upon
these prisoners’ release, even when that harm might arise
from conduct that is otherwise beyond the general regula
tory powers of the federal government” (emphasis added)).
——————
   5 For the reasons explained in Part III–A–2, infra, the enumerated

power that justifies a particular defendant’s criminal arrest or convic
tion cannot justify his subsequent civil detention under §4248.
8                  UNITED STATES v. COMSTOCK

                         THOMAS, J., dissenting

  To be sure, protecting society from violent sexual of
fenders is certainly an important end. Sexual abuse is a
despicable act with untold consequences for the victim
personally and society generally. See, e.g., Kennedy v.
Louisiana, 554 U. S. ___, ___, n. 2, (2008) (ALITO, J., dis
senting) (slip op., at 9, n. 2, 22–23). But the Constitution
does not vest in Congress the authority to protect society
from every bad act that might befall it.6 New York v.
United States, 505 U. S. 144, 157 (1992) (“ ‘The question is
not what power the Federal Government ought to have
but what powers in fact have been given by the people’ ”
(quoting United States v. Butler, 297 U. S. 1, 63 (1936)).
  In my view, this should decide the question. Section
4248 runs afoul of our settled understanding of Congress’
power under the Necessary and Proper Clause. Congress
may act under that Clause only when its legislation
“carr[ies] into Execution” one of the Federal Government’s
enumerated powers. Art. I, §8, cl. 18. Section 4248 does
not execute any enumerated power. Section 4248 is there
fore unconstitutional.
                             III
   The Court perfunctorily genuflects to McCulloch’s
framework for assessing Congress’ Necessary and Proper
Clause authority, and to the principle of dual sovereignty
it helps to maintain, then promptly abandons both in favor
of a novel five-factor test supporting its conclusion that
§4248 is a “ ‘necessary and proper’ ” adjunct to a jumble of
unenumerated “authorit[ies].” Ante, at 22. The Court’s
newly minted test cannot be reconciled with the Clause’s
plain text or with two centuries of our precedents inter
——————
  6 The absence of a constitutional delegation of general police power to

Congress does not leave citizens vulnerable to the harms Congress
seeks to regulate in §4248 because, as recent legislation indicates, the
States have the capacity to address the threat that sexual offenders
pose. See n. 15, infra.
                 Cite as: 560 U. S. ____ (2010)           9

                    THOMAS, J., dissenting

preting it. It also raises more questions than it answers.
Must each of the five considerations exist before the Court
sustains future federal legislation as proper exercises of
Congress’ Necessary and Proper Clause authority? What
if the facts of a given case support a finding of only four
considerations? Or three? And if three or four will suffice,
which three or four are imperative? At a minimum, this
shift from the two-step McCulloch framework to this five
consideration approach warrants an explanation as to why
McCulloch is no longer good enough and which of the five
considerations will bear the most weight in future cases,
assuming some number less than five suffices. (Or, if not,
why all five are required.) The Court provides no answers
to these questions.
                            A
  I begin with the first and last “considerations” in the
Court’s inquiry. Ante, at 5. The Court concludes that
§4248 is a valid exercise of Congress’ Necessary and
Proper Clause authority because that authority is “broad,”
ibid., and because “the links between §4248 and an enu
merated Article I power are not too attenuated,” ante, at
18. In so doing, the Court first inverts, then misapplies,
McCulloch’s straightforward two-part test.
                             1
                             a
  First, the Court describes Congress’ lawmaking power
under the Necessary and Proper Clause as “broad,” relying
on precedents that have upheld federal laws under the
Clause after finding a “ ‘rationa[l]’ ” fit between the law
and an enumerated power. Ante, at 6 (quoting Sabri v.
United States, 541 U. S. 600, 605 (2004)). It is true that
this Court’s precedents allow Congress a certain degree of
latitude in selecting the means for “carrying into Execu
10                 UNITED STATES v. COMSTOCK

                         THOMAS, J., dissenting

tion” an end that is “legitimate.”7 See, e.g., Jinks v. Rich
land County, 538 U. S. 456, 462–463 (2003) (citing
McCulloch, 4 Wheat., at 417, 421). But in citing these
cases, the Court puts the cart before the horse: The fit
between means and ends matters only if the end is in fact
legitimate—i.e., only if it is one of the Federal Govern
ment’s enumerated powers.
   By starting its inquiry with the degree of deference
owed to Congress in selecting means to further a legiti
mate end, the Court bypasses McCulloch’s first step and
fails carefully to examine whether the end served by §4248
is actually one of those powers. See Part III–A–2, infra.
                             b
  Second, instead of asking the simple question of what
enumerated power §4248 “carr[ies] into Execution” at
McCulloch’s first step, the Court surveys other laws Con
gress has enacted and concludes that, because §4248 is
related to those laws, the “links” between §4248 and an
enumerated power are not “too attenuated”; hence, §4248
is a valid exercise of Congress’ Necessary and Proper
Clause authority. Ante, at 18. This unnecessarily con
fuses the analysis and, if followed to its logical extreme,
would result in an unwarranted expansion of federal
——————
  7 JUSTICE KENNEDY concludes that the Necessary and Proper Clause
requires something beyond rational-basis scrutiny when assessing the
fit between an enumerated power and the means Congress selects to
execute it. Ante, at 2–4 (opinion concurring in judgment). Other
arguments regarding the degree of fit between means and end have
been lodged elsewhere. See, e.g., Gonzales v. Raich, 545 U. S. 1, 61
(2005) (THOMAS, J., dissenting) (arguing that, for a law to be within the
Necessary and Proper Clause, it must bear an “ ‘obvious, simple, and
direct relation’ ” to an exercise of Congress’ enumerated powers and
must not subvert basic principles of federalism and dual sovereignty).
But I find that debate beside the point here, because it concerns the
analysis employed at McCulloch’s second step, see McCulloch v. Mary
land, 4 Wheat. 316 (1819), while the Court’s decision today errs by
skipping the first.
                     Cite as: 560 U. S. ____ (2010)                   11

                         THOMAS, J., dissenting

power.
   The Court observes that Congress has the undisputed
authority to “criminalize conduct” that interferes with
enumerated powers; to “imprison individuals who engage
in that conduct”; to “enact laws governing [those] prisons”;
and to serve as a “custodian of its prisoners.” Ante, at 9,
14. From this, the Court assumes that §4248 must also be
a valid exercise of congressional power because it is “ ‘rea
sonably adapted’ ” to those exercises of Congress’ inciden
tal—and thus unenumerated—authorities. See ante, at 15
(concluding that “§4248 is ‘reasonably adapted’ to Con
gress’ power to act as a responsible federal custodian”
(citation omitted)); ante, at 22 (concluding that “the stat
ute is a ‘necessary and proper’ means of exercising the
federal authority that permits Congress to create federal
criminal laws, to punish their violation, to imprison viola
tors, to provide appropriately for those imprisoned, and to
maintain the security of those who are not imprisoned but
who may be affected by the federal imprisonment of oth
ers”). But that is not the question. The Necessary and
Proper Clause does not provide Congress with authority to
enact any law simply because it furthers other laws Con
gress has enacted in the exercise of its incidental author
ity; the Clause plainly requires a showing that every
federal statute “carr[ies] into Execution” one or more of
the Federal Government’s enumerated powers.8
——————
  8 McCulloch   makes this point clear. As the Court notes, ante, at 18–
19, McCulloch states, in discussing a hypothetical, that from Congress’
enumerated power to establish post offices and post roads “has been
inferred the power and duty of carrying the mail,” and, “from this
implied power, has again been inferred the right to punish those who
steal letters from the post office, or rob the mail.” 4 Wheat., at 417.
Contrary to the Court’s interpretation, this dictum does not suggest
that the relationship between Congress’ implied power to punish postal
crimes and its implied power to carry the mail is alone sufficient to
satisfy review under the Necessary and Proper Clause. Instead,
McCulloch directly links the constitutionality of the former to Congress’
12                 UNITED STATES v. COMSTOCK

                         THOMAS, J., dissenting

  Federal laws that criminalize conduct that interferes
with enumerated powers, establish prisons for those who
engage in that conduct, and set rules for the care and
treatment of prisoners awaiting trial or serving a criminal
sentence satisfy this test because each helps to “carr[y]
into Execution” the enumerated powers that justify a
criminal defendant’s arrest or conviction. For example,
Congress’ enumerated power “[t]o establish Post Offices
and post Roads,” Art. I, §8, cl. 7, would lack force or practi
cal effect if Congress lacked the authority to enact crimi
nal laws “to punish those who steal letters from the post
office, or rob the mail.” McCulloch, supra, at 417. Simi
larly, that enumerated power would be compromised if
there were no prisons to hold persons who violate those
laws, or if those prisons were so poorly managed that
prisoners could escape or demand their release on the
grounds that the conditions of their confinement violate
their constitutional rights, at least as we have defined
them. See, e.g., Estelle v. Gamble, 429 U. S. 97 (1976).
——————
enumerated power “ ‘to establish post offices and post roads.’ ” Ibid.
(explaining that “the right to . . . punish those who rob [the mail] is not
indispensably necessary to the establishment of a post office and post
road,” but is “essential to the beneficial exercise of th[at] power”). More
importantly, McCulloch’s holding, as well as the holdings of this Court’s
subsequent decisions, make plain that congressional action is valid
under the Necessary and Proper Clause only if it carries into execution
one or more enumerated powers. Id., at 422 (upholding Congress’
incorporation of a bank because it was a “means . . . to be employed
only for the purpose of carrying into execution the given powers” (em
phasis added)); see Sabri v. United States, 541 U. S. 600, 605 (2004)
(“Congress has authority under the Spending Clause to appropriate
federal moneys to promote the general welfare, and it has correspond
ing authority under the Necessary and Proper Clause to see to it that
taxpayer dollars appropriated under that power are in fact spent for the
general welfare” (emphasis added; citations omitted)); Stewart v. Kahn,
11 Wall. 493, 506–507 (1871) (“The power to pass [the Act in question]
is necessarily implied from the powers to make war and suppress
insurrections” (emphasis added) (referring to Art. I, §8, cls. 11 and 15)).
                     Cite as: 560 U. S. ____ (2010)                  13

                        THOMAS, J., dissenting

Civil detention under §4248, on the other hand, lacks any
such connection to an enumerated power.
                               2
   After focusing on the relationship between §4248 and
several of Congress’ implied powers, the Court finally
concludes that the civil detention of a “sexually dangerous
person” under §4248 carries into execution the enumer
ated power that justified that person’s arrest or conviction
in the first place. In other words, the Court analogizes
§4248 to federal laws that authorize prison officials to care
for federal inmates while they serve sentences or await
trial. But while those laws help to “carr[y] into Execution”
the enumerated power that justifies the imposition of
criminal sanctions on the inmate, §4248 does not bear that
essential characteristic for three reasons.
   First, the statute’s definition of a “sexually dangerous
person” contains no element relating to the subject’s
crime. See §§4247(a)(5)–(6). It thus does not require a
federal court to find any connection between the reasons
supporting civil commitment and the enumerated power
with which that person’s criminal conduct interfered. As a
consequence, §4248 allows a court to civilly commit an
individual without finding that he was ever charged with
or convicted of a federal crime involving sexual violence.
§§4248(a), (d). That possibility is not merely hypothetical:
The Government concedes that nearly 20% of individuals
against whom §4248 proceedings have been brought fit
this description.9 Tr. of Oral Arg. 23–25.
   Second, §4248 permits the term of federal civil commit
ment to continue beyond the date on which a convicted
——————
  9 The statute does require the court to find that the subject “has en

gaged or attempted to engage in sexually violent conduct or child
molestation,” §4247(a)(5), but that factual predicate can be established
by a state conviction, or by clear and convincing evidence that the
person committed a sex crime for which he was never charged.
14             UNITED STATES v. COMSTOCK

                    THOMAS, J., dissenting

prisoner’s sentence expires or the date on which the stat
ute of limitations on an untried defendant’s crime has run.
The statute therefore authorizes federal custody over a
person at a time when the Government would lack juris
diction to detain him for violating a criminal law that
executes an enumerated power.
   The statute this Court upheld in Greenwood v. United
States, 350 U. S. 366 (1956), provides a useful contrast.
That statute authorized the Federal Government to exer
cise civil custody over a federal defendant declared men
tally unfit to stand trial only “ ‘until the accused shall be
mentally competent to stand trial or until the pending
charges against him are disposed of according to law.’ ”
Id., at 368, n. 2 (quoting 18 U. S. C. §4246 (1952 ed.)).
Thus, that statute’s “end” reasonably could be interpreted
as preserving the Government’s power to enforce a crimi
nal law against the accused. Section 4248 (2006 ed.),
however, authorizes federal detention of a person even
after the Government loses the authority to prosecute him
for a federal crime.
   Third, the definition of a “sexually dangerous person”
relevant to §4248 does not require the court to find that
the person is likely to violate a law executing an enumer
ated power in the future. Although the Federal Govern
ment has no express power to regulate sexual violence
generally, Congress has passed a number of laws proscrib
ing such conduct in special circumstances. All of these
statutes contain jurisdictional elements that require a
connection to one of Congress’ enumerated powers—such
as interstate commerce, e.g., §2252(a)(2)—or that limit the
statute’s coverage to jurisdictions in which Congress has
plenary authority, e.g., §2243(a). Section 4248, by con
trast, authorizes civil commitment upon a showing that
the person is “sexually dangerous,” and presents a risk “to
others,” §4247(a)(5). It requires no evidence that this
sexually dangerous condition will manifest itself in a way
                      Cite as: 560 U. S. ____ (2010)                       15

                          THOMAS, J., dissenting

that interferes with a federal law that executes an enu
merated power or in a geographic location over which
Congress has plenary authority.10
  In sum, the enumerated powers that justify a criminal
defendant’s arrest or conviction cannot justify his subse
quent civil detention under §4248.
                              B
  The remaining “considerations” in the Court’s five-part
inquiry do not alter this conclusion.
                              1
  First, in a final attempt to analogize §4248 to laws that
authorize the Federal Government to provide care and
treatment to prisoners while they await trial or serve a
criminal sentence, the Court cites the Second Restatement
of Torts for the proposition that the Federal Government
has a “custodial interest” in its prisoners, ante, at 22, and,
thus, a broad “constitutional power to act in order to pro
tect nearby (and other) communities” from the dangers
——————
   10 The Constitution grants Congress plenary authority over certain

jurisdictions where no other sovereign exists, including the District of
Columbia, Art. I, §8, cl. 17, and federal territories, Art. IV, §3, cl. 2. In
addition, Congress has “broad general powers to legislate in respect to
Indian tribes,” United States v. Lara, 541 U. S. 193, 200 (2004) (citing
Art. I, §8, cl. 3; Art. II, §2, cl. 2), including certain special responsibili
ties over “Indian country,” 18 U. S. C. §1151. Although the Necessary
and Proper Clause did not authorize Congress to enact §4248, I do not
rule out the possibility that Congress could provide for the civil com
mitment of individuals who enter federal custody as a result of acts
committed in these jurisdictions. See, e.g., United States v. Cohen, 733
F. 2d 128 (CADC 1984) (en banc) (upholding civil commitment of a
defendant under a District of Columbia statute authorizing the institu
tionalization of persons acquitted by reason of insanity). Although two
of the respondents in this case were either charged with or convicted of
criminal acts committed in such jurisdictions, see ante, at 3; 507
F. Supp. 2d 522, 527, and n. 2 (EDNC 2007), that question is not
presented here because §4248 does not make that fact essential to an
individual’s placement in civil detention.
16                UNITED STATES v. COMSTOCK

                        THOMAS, J., dissenting

they may pose,11 ante, at 14. That citation is puzzling
because federal authority derives from the Constitution,
not the common law. In any event, nothing in the Re
statement suggests that a common-law custodian has the
powers that Congress seeks here. While the Restatement
provides that a custodian has a duty to take reasonable
steps to ensure that a person in his care does not cause
“bodily harm to others,” 2 Restatement (Second) of Torts
§319, p. 129 (1963–1964), that duty terminates once the
legal basis for custody expires:
     “There is no duty so to control the conduct of a third
     person as to prevent him from causing physical harm
     to another unless
        “(a) a special relation exists between the actor and
     the third person which imposes a duty upon the actor
     to control the third person’s conduct, or
        “(b) a special relation exists between the actor and
     the other which gives to the other a right to protec
     tion.” Id., §315, at 122.
Once the Federal Government’s criminal jurisdiction over
a prisoner ends, so does any “special relation[ship]” be
tween the Government and the former prisoner.12
——————
  11 The Court also cites Youngberg v. Romeo, 457 U. S. 307 (1982), but

that case lends even less support than the Restatement. In Youngberg,
an inmate at a state hospital argued that hospital workers violated his
constitutional rights when they applied restraints to keep him in his
bed at the hospital infirmary. Id., at 310–311. In assessing that claim,
this Court noted that the hospital had a responsibility to “protect its
residents” from the danger of violence. Id., at 320 (emphasis added).
The Court never suggested that this responsibility extended to “nearby
(and other) communities.” Ante, at 14. Moreover, the hospital was a
state institution. Nothing in Youngberg suggests that the Federal
Government can detain a person beyond the date on which its criminal
jurisdiction expires for fear that he may later pose a threat to the
surrounding community.
  12 Federal law permits a sentencing court to order that a defendant be

placed on a term of “supervised release” after his term of imprisonment
                     Cite as: 560 U. S. ____ (2010)                  17

                        THOMAS, J., dissenting

   For this reason, I cannot agree with JUSTICE ALITO that
§4248 is a necessary and proper incident of Congress’
power “to protect the public from dangers created by the
federal criminal justice and prison systems.” Ante, at 3
(concurring in judgment). A federal criminal defendant’s
“sexually dangerous” propensities are not “created by” the
fact of his incarceration or his relationship with the fed
eral prison system. The fact that the Federal Government
has the authority to imprison a person for the purpose of
punishing him for a federal crime—sex-related or other
wise—does not provide the Government with the addi
tional power to exercise indefinite civil control over that
person.13
                             2
  Second, the Court describes §4248 as a “modest” expan
sion on a statutory framework with a long historical pedi
gree. Ante, at 9. Yet even if the antiquity of a practice
could serve as a substitute for its constitutionality—and
the Court admits that it cannot, ibid.—the Court over
states the relevant history.
  Congress’ first foray into this general area occurred in
1855, when it established St. Elizabeth’s Hospital to pro
vide treatment to “insane” persons in the military and the
——————
is complete. 18 U. S. C. §§3583, 3624(e). Contrary to the Government’s
suggestion, federal authority to exercise control over individuals
serving terms of “supervised release” does not derive from the Govern
ment’s “relationship” with the prisoner, see Brief for United States 38,
but from the original criminal sentence itself. Supervised release thus
serves to execute the enumerated power that justifies the defendant’s
statute of conviction, just like any other form of punishment imposed at
sentencing.
   13 The fact that Congress has the authority to “provide for the appre

hension of escaped federal prisoners,” see ante, at 3 (ALITO, J., concur
ring in judgment), does not change this conclusion. That authority
derives from Congress’ power to vindicate the enumerated power with
which the escaped defendant’s crime of conviction interfered, not a
freestanding police power.
18                UNITED STATES v. COMSTOCK

                        THOMAS, J., dissenting

District of Columbia. Act of Mar. 3, 1855, 10 Stat. 682.
But Congress was acting pursuant to enumerated powers
when it took this step. See Art. I, §8, cl. 17 (granting
Congress plenary authority over the District of Columbia);
Art. I, §8, cl. 14 (authorizing Congress to “make Rules for
the Government and Regulation of the land and naval
Forces”). This enactment therefore provides no support
for Congress’ claimed power to detain sexually dangerous
persons without an otherwise valid basis for jurisdiction.
  Later, Congress provided for the federal civil commit
ment of “insane” persons charged with or convicted of a
federal crime. Act of Feb. 7, 1857, §§5–6, 11 Stat. 158; see
17 Op. Atty. Gen. 211, 212–213 (1881); Act of June 23,
1874, ch. 465, 18 Stat. 251; Act of Aug. 7, 1882, 22 Stat.
330. As the Court explains, however, these statutes did
not authorize federal custody beyond the completion of the
“term” of federal “imprisonment,” §§2–3, 18 Stat. 252; see
35 Op. Atty. Gen. 366, 368 (1927); 30 Op. Atty. Gen. 569,
570–571 (1916); Act of May 13, 1930, ch. 254, §6, 46 Stat.
271, and thus shed no light on the question presented
here.
  In 1949, Congress enacted a more comprehensive re
gime, authorizing the civil commitment of mentally ill
persons in BOP custody. See 18 U. S. C. §§4246, 4247
(1952 ed.). This Court addressed that regime in Green
wood, but never endorsed the proposition that the Federal
Government could rely on that statute to detain a person
in the absence of a pending criminal charge or ongoing
criminal sentence.14
——————
  14 In addition, at least some courts questioned the Federal Govern

ment’s power to detain a person in such circumstances. See Dixon v.
Steele, 104 F. Supp. 904, 908 (WD Mo. 1952) (holding that the Federal
Government lacked authority to detain an individual declared mentally
unfit to stand trial once it was determined that he was unlikely to
recover in time to be prosecuted); Higgins v. United States, 205 F. 2d
650, 653 (CA9 1953) (avoiding this constitutional question by interpret
                     Cite as: 560 U. S. ____ (2010)                  19

                        THOMAS, J., dissenting

   As already noted, Greenwood upheld the commitment of
a federal defendant declared unfit to stand trial on the
narrow ground that the Government’s criminal jurisdic
tion over the defendant—its “power to prosecute for fed
eral offenses—[wa]s not exhausted,” but rather “per
sist[ed]” in the form of a “pending indictment.” 350 U. S.,
at 375; see supra, at 16. The Court was careful to state
that “[t]his commitment, and therefore the legislation
authorizing commitment in the context of this case, in
volve[d] an assertion of authority” within “congressional
power under the Necessary and Proper Clause.” Green
wood, 350 U. S., at 375 (emphasis added). But it painstak
ingly limited its holding to “the narrow constitutional
issue raised by th[at] order of commitment.” Ibid.
   The historical record thus supports the Federal Gov
ernment’s authority to detain a mentally ill person against
whom it has the authority to enforce a criminal law. But
it provides no justification whatsoever for reading the
Necessary and Proper Clause to grant Congress the power
to authorize the detention of persons without a basis for
federal criminal jurisdiction.
                              3
  Finally, the Court offers two arguments regarding
§4248’s impact on the relationship between the Federal
Government and the States. First, the Court and both
concurrences suggest that Congress must have had the
power to enact §4248 because a long period of federal
incarceration might “seve[r]” a sexually dangerous pris
oner’s “claim to ‘legal residence’ ” in any particular State,
ante, at 15 (opinion of the Court), thus leaving the pris
oner without any “home State to take charge” of him upon
release, ante, at 5 (KENNEDY, J., concurring in judgment);
——————
ing the statute to permit federal civil detention only for a period rea
sonably related to a criminal prosecution); Wells v. Attorney General of
United States, 201 F. 2d 556, 560 (CA10 1953) (same).
20                 UNITED STATES v. COMSTOCK

                         THOMAS, J., dissenting

see ante, at 1 (ALITO, J., concurring in judgment) (noting
that many federal prisoners, “as a result of lengthy federal
incarceration, no longer ha[ve] any substantial ties to any
State”). I disagree with the premise of that argument. As
an initial matter, States plainly have the constitutional
authority to “take charge” of a federal prisoner released
within their jurisdiction. See Amdt. 10 (stating that pow
ers not delegated to the Federal Government are “re
served” to the States, and to the people). In addition, the
assumption that a State knowingly would fail to exercise
that authority is, in my view, implausible. The Govern
ment stated at oral argument that its “default position” is
to release a federal prisoner to the State in which he was
convicted, Tr. of Oral Arg. 15; see also 28 CFR §2.33(b)
(2009), and neither the Court nor the concurrences argue
that a State has the power to refuse such a person domi
cile within its borders. Thus, they appear to assume that,
in the absence of 18 U. S. C. §4248, a State would take no
action when informed by the BOP that a sexually danger
ous federal prisoner was about to be released within its
jurisdiction. In light of the plethora of state laws enacted
in recent decades to protect communities from sex offend
ers,15 the likelihood of such an occurrence seems quite
——————
  15 As we have noted before, all 50 States have developed “some varia
tion” of a system “for mandatory registration of sex offenders and
corresponding community notification.” Smith v. Doe, 538 U. S. 84, 89–
90 (2003). In addition, several States have taken further steps; some
impose residency restrictions on sex offenders, see, e.g., Kennedy v.
Louisiana, 554 U. S. ___ , ___, n. 5 (2008) (ALITO, J., dissenting) (slip
op., at 11, n. 5) (collecting statutes), and, most relevant here, 22 States
have enacted involuntary civil-commitment laws substantially similar
to §4248, see Ariz. Rev. Stat. Ann. §36–3701 et seq. (West 2009); Cal.
Welf. & Inst. Code Ann. §6600 et seq. (West 1988 and Supp. 2010); Fla.
Stat. §394.910 et seq. (2007); Ill. Comp. Stat. Ann., ch. 725, §205 et seq.
(West 2008); Iowa Code §229A (2009); Kan. Stat. Ann. §59–29a01 et
seq. (2005 and 2008 Cum. Supp.); Mass. Gen. Laws, ch. 123A (West
2008); Minn. Stat. §253B (2008 and 2009 Supp.); Mo. Rev. Stat.
                     Cite as: 560 U. S. ____ (2010)                   21

                         THOMAS, J., dissenting

remote. But even in the event a State made such a deci
sion, the Constitution assigns the responsibility for that
decision, and its consequences, to the state government
alone.
   Next, the Court submits that §4248 does not upset the
balance of federalism or invade the States’ reserved pow
ers because it “requires accommodation of state interests”
by instructing the Attorney General to release a commit
ted person to the State in which he was domiciled or tried
if that State wishes to “ ‘assume . . . responsibility’ ” for
him. Ante, at 17 (quoting §4248(d)). This right of first
refusal is mere window dressing. Tr. of Oral Arg. 5 (“It is
not the usual course that the State does take responsibil
ity”). More importantly, it is an altogether hollow assur
ance that §4248 preserves the principle of dual sover
eignty—the “letter and spirit” of the Constitution—as the
Necessary and Proper Clause requires.16 McCulloch, 4
——————
§632.480 et seq. (2009 Cum. Supp.); Neb. Rev. Stat. §29–2923 et seq.
(2008); N. H. Rev. Stat. Ann. §135–E:1 et seq. (West Supp. 2009); N. J.
Stat. Ann. §30:4–82.4 et seq. (West 2008); N. M. Stat. Ann. §43–1–1 et
seq. (2000 and Supp. 2009); N. Y. Mental Hyg. Law Ann. §10.01 et seq.
(West Supp. 2010); N. D. Cent. Code §25–03.3–01 et seq. (2002 and
Supp. 2009); Ore. Rev. Stat. §426.510 et seq. (2007); S. C. Code Ann.
§44–48–10 et seq. (Supp. 2009); Tenn. Code Ann. §33–6–801 et seq.
(2007); Tex. Health & Safety Code Ann. §841.001 et seq. (West 2009);
Va. Code Ann. §37.2–900 et seq. (Lexis Supp. 2009); Wash. Rev. Code
§71.09.010 et seq. (2008); Wis. Stat. Ann. §980.01 et seq. (West 2007 and
Supp. 2009).
   16 The Court describes my argument as a claim that “§4248 violates

the Tenth Amendment.” Ante, at 16. Yet, I agree entirely with the
Court that “ ‘it makes no difference whether one views the question at
issue [here] as one of ascertaining the limits of the power delegated to
the Federal Government under the affirmative provisions of the Consti
tution or one of discerning the core of sovereignty retained by the
States under the Tenth Amendment.’ ” Ibid. (quoting New York v.
United States, 505 U. S. 144, 159 (1992)). Section 4248 is unconstitu
tional because it does not “carr[y] into Execution” an enumerated
power. Therefore, it necessarily intrudes upon the powers our Consti
tution reserves to the States and to the people.
22             UNITED STATES v. COMSTOCK

                    THOMAS, J., dissenting

Wheat., at 421; Printz v. United States, 521 U. S. 898,
923–924 (1997). For once it is determined that Congress
has the authority to provide for the civil detention of
sexually dangerous persons, Congress “is acting within the
powers granted it under the Constitution,” and “may
impose its will on the States.” Gregory, 501 U. S., at 460;
see Art. VI, cl. 2. Section 4248’s right of first refusal is
thus not a matter of constitutional necessity, but an act of
legislative grace.
   Nevertheless, 29 States appear as amici and argue that
§4248 is constitutional. They tell us that they do not
object to Congress retaining custody of “sexually danger
ous persons” after their criminal sentences expire because
the cost of detaining such persons is “expensive”—
approximately $64,000 per year—and these States would
rather the Federal Government bear this expense. Brief
for Kansas et al. 2; ibid. (“[S]ex offender civil commitment
programs are expensive to operate”); id., at 4 (“these pro
grams are expensive”); id., at 8 (“[T]here are very practical
reasons to prefer a system that includes a federal sex
offender civil commitment program . . . . One such reason
is the significant cost”).
   Congress’ power, however, is fixed by the Constitution;
it does not expand merely to suit the States’ policy prefer
ences, or to allow State officials to avoid difficult choices
regarding the allocation of state funds. By assigning the
Federal Government power over “certain enumerated
objects only,” the Constitution “leaves to the several States
a residuary and inviolable sovereignty over all other ob
jects.” The Federalist No. 39, at 285 (J. Madison). The
purpose of this design is to preserve the “balance of power
between the States and the Federal Government . . . [that]
protect[s] our fundamental liberties.” Garcia v. San Anto
nio Metropolitan Transit Authority, 469 U. S. 528, 572
(1985) (Powell, J., dissenting); New York v. United States,
505 U. S., at 181. It is the States’ duty to act as the “im
                  Cite as: 560 U. S. ____ (2010)            23

                     THOMAS, J., dissenting

mediate and visible guardian” of those liberties because
federal powers extend no further than those enumerated
in the Constitution. The Federalist No. 17, at 169 (A.
Hamilton). The Constitution gives States no more power
to decline this responsibility than it gives them to infringe
upon those liberties in the first instance. FTC v. Ticor
Title Ins. Co., 504 U. S. 621, 636 (1992) (“Federalism
serves to assign political responsibility, not to obscure it”).
  Absent congressional action that is in accordance with,
or necessary and proper to, an enumerated power, the
duty to protect citizens from violent crime, including acts
of sexual violence, belongs solely to the States. Morrison,
529 U. S., at 618 (“[W]e can think of no better example of
the police power, which the Founders denied the National
Government and reposed in the States, than the suppres
sion of violent crime”); see Cohens v. Virginia, 6 Wheat.
264, 426 (1821) (Marshall, C. J.) (stating that Congress
has “no general right to punish murder committed within
any of the States”).
                         *    *     *
  Not long ago, this Court described the Necessary and
Proper Clause as “the last, best hope of those who defend
ultra vires congressional action.” Printz, supra, at 923.
Regrettably, today’s opinion breathes new life into that
Clause, and—the Court’s protestations to the contrary
notwithstanding, see ante, at 18—comes perilously close to
transforming the Necessary and Proper Clause into a
basis for the federal police power that “we always have
rejected,” Lopez, 514 U. S., at 584 (THOMAS, J., concur
ring) (citing Gregory, supra, at 457; Wirtz, 392 U. S., at
196; Jones & Laughlin Steel Corp., 301 U. S., at 37). In so
doing, the Court endorses the precise abuse of power
Article I is designed to prevent—the use of a limited grant
of authority as a “pretext . . . for the accomplishment of
objects not intrusted to the government.” McCulloch,
supra, at 423.
  I respectfully dissent.
