                          PUBLISHED

UNITED STATES COURT OF APPEALS
                FOR THE FOURTH CIRCUIT


JOSE PADILLA,                            
                  Petitioner-Appellee,
                  v.
C. T. HANFT, U.S.N. Commander,
Consolidated Naval Brig.,
               Respondent-Appellant.


WASHINGTON LEGAL FOUNDATION; THE
ALLIED EDUCATIONAL FOUNDATION,
         Amici Supporting Appellant,
NATIONAL ASSOCIATION OF CRIMINAL
DEFENSE LAWYERS; COMPARATIVE LAW
SCHOLARS AND EXPERTS ON THE
LAWS OF THE UNITED KINGDOM AND
ISRAEL; PEOPLE FOR THE AMERICAN             No. 05-6396
WAY FOUNDATION AND THE RUTHERFORD
INSTITUTE; THE BRENNAN CENTER FOR
JUSTICE AT THE NEW YORK UNIVERSITY
SCHOOL OF LAW; AMERICAN CIVIL
LIBERTIES UNION; NEW YORK CIVIL
LIBERTIES UNION; AMERICAN CIVIL
LIBERTIES UNION OF SOUTH CAROLINA;
AMERICAN CIVIL LIBERTIES UNION OF
VIRGINIA; ORIGINAL CONGRESSIONAL
SPONSORS OF 18 U.S.C. SECTION
4001(A); JANET RENO; PHILIP B.
HEYMANN; ERIC H. HOLDER, JR.;
JEFFREY H. SMITH; CENTER FOR
NATIONAL SECURITY STUDIES;
CONSTITUTION PROJECT,
            Amici Supporting Appellee.   
2                         PADILLA v. HANFT
           Appeal from the United States District Court
         for the District of South Carolina, at Charleston.
                  Henry F. Floyd, District Judge.
                        (CA-04-2221-26AJ)

                       Argued: July 19, 2005

                    Decided: September 9, 2005

    Before LUTTIG, MICHAEL, and TRAXLER, Circuit Judges.



Reversed by published opinion. Judge Luttig wrote the opinion for the
Court, in which Judge Michael and Judge Traxler joined.


                            COUNSEL

ARGUED: Paul Clement, UNITED STATES DEPARTMENT OF
JUSTICE, Department of the Solicitor, Washington, D.C., for Appel-
lant. Andrew G. Patel, New York, New York, for Appellee. ON
BRIEF: Jonathan S. Gasser, United States Attorney, OFFICE OF
THE UNITED STATES ATTORNEY, Columbia, South Carolina;
Miller W. Shealy, Jr., Assistant United States Attorney, OFFICE OF
THE UNITED STATES ATTORNEY, Charleston, South Carolina;
David B. Salmons, Assistant to the Solicitor General, Daryl Joseffer,
Assistant to the Solicitor General, Stephan E. Oestreicher, Jr.,
UNITED STATES DEPARTMENT OF JUSTICE, Washington,
D.C., for Appellant. Jenny S. Martinez, Stanford, California; Michael
P. O’Connell, STIRLING & O’CONNELL, Charleston, South Caro-
lina; Donna R. Newman, New York, New York; Jonathan M. Frei-
man, WIGGIN AND DANA, L.L.P., New Haven, Connecticut, for
Appellee. Daniel J. Popeo, Richard A. Samp, WASHINGTON
LEGAL FOUNDATION, Washington, D.C., for Amici Curiae,
Washington Legal Foundation and The Allied Educational Founda-
tion, Supporting Appellant. Steven D. Benjamin, BENJAMIN &
DESPORTES, P.C., Richmond, Virginia; Donald G. Rehkopf, Jr.,
BRENNA & BRENNA, P.L.L.C., Rochester, New York, for Amicus
                         PADILLA v. HANFT                         3
Curiae, National Association of Criminal Defense Lawyers, Support-
ing Appellee. David N. Rosen, DAVID ROSEN & ASSOCIATES,
P.C., New Haven, Connecticut; Mary J. Hahn, ALLARD K.
LOWENSTEIN INTERNATIONAL HUMAN RIGHTS CLINIC,
New Haven, Connecticut, for Amicus Curiae, Comparative Law
Scholars and Experts on the Laws of the United Kingdom and Israel,
Supporting Appellee. Elliot M. Mincberg, Deborah Liu, PEOPLE
FOR THE AMERICAN WAY FOUNDATION, Washington, D.C.;
John W. Whitehead, THE RUTHERFORD INSTITUTE, Charlottes-
ville, Virginia; Mark E. Haddad, Joseph R. Guerra, Robert N. Hoch-
man, Chad W. Pekron, SIDLEY, AUSTIN, BROWN & WOOD,
L.L.P., Washington, D.C., for Amici Curiae, People for the American
Way Foundation and The Rutherford Institute, Supporting Appellee.
Serrin Turner, Burt Neuborne, BRENNAN CENTER FOR JUSTICE,
New York University School of Law, New York, New York, for
Amicus Curiae, The Brennan Center for Justice at the New York Uni-
versity School of Law, Supporting Appellee. Ann Beeson, AMERI-
CAN CIVIL LIBERTIES UNION FOUNDATION, New York, New
York; Denyse Williams, ACLU OF SOUTH CAROLINA, Columbia,
South Carolina; Arthur N. Eisenberg, NEW YORK CIVIL LIBER-
TIES UNION FOUNDATION, New York, New York; Rebecca K.
Glenberg, ACLU OF VIRGINIA FOUNDATION, Richmond, Vir-
ginia, for Amici Curiae, American Civil Liberties Union, New York
Civil Liberties Union, American Civil Liberties Union of South Caro-
lina, American Civil Liberties Union of Virginia, Incorporated, Sup-
porting Appellee. Matthew S. Dontzin, Brian S. Koukoutchos, Fiona
M. Doherty, THE DONTZIN LAW FIRM, L.L.P., New York, New
York, for Amici Curiae, Original Congressional Sponsors of 18
U.S.C. Section 4001(A), Supporting Appellee. Julia C. Ambrose,
Katherine E. Stern, JONES DAY, Washington, D.C.; Deborah N.
Pearlstein, Avidan Y. Cover, HUMAN RIGHTS FIRST, New York,
New York, for Amici Curiae, Janet Reno, Philip B. Heymann, Eric
H. Holder, Jr., and Jeffrey H. Smith, Supporting Appellee. Kate Mar-
tin, CENTER FOR NATIONAL SECURITY STUDIES, Washington,
D.C.; Joseph Onek, THE CONSTITUTION PROJECT, Washington,
D.C.; Paul R. Q. Wolfson, WILMER, CUTLER, PICKERING,
HALE AND DORR, L.L.P., Washington, D.C.; Kate Hutchins, WIL-
MER, CUTLER, PICKERING, HALE AND DORR, L.L.P., New
4                          PADILLA v. HANFT
York, New York, for Amici Curiae, Center for National Security
Studies and Constitution Project, Supporting Appellee.



                              OPINION

LUTTIG, Circuit Judge:

   Appellee Jose Padilla, a United States citizen, associated with
forces hostile to the United States in Afghanistan and took up arms
against United States forces in that country in our war against al
Qaeda. Upon his escape to Pakistan from the battlefield in Afghani-
stan, Padilla was recruited, trained, funded, and equipped by al Qaeda
leaders to continue prosecution of the war in the United States by
blowing up apartment buildings in this country. Padilla flew to the
United States on May 8, 2002, to begin carrying out his assignment,
but was arrested by civilian law enforcement authorities upon his
arrival at O’Hare International Airport in Chicago.

   Thereafter, in a letter to the Secretary of Defense, the President of
the United States personally designated Padilla an "enemy combatant"
against this country, stating that the United States is "at war" with al
Qaeda, that "Mr. Padilla engaged in conduct that constituted hostile
and war-like acts, including conduct in preparation for acts of interna-
tional terrorism that had the aim to cause injury to or adverse effects
on the United States," and that "Mr. Padilla represents a continuing,
present and grave danger to the national security of the United
States." Having determined that "detention of Mr. Padilla is necessary
to prevent him from aiding al Qaeda in its efforts to attack the United
States or its armed forces, other governmental personnel, or citizens,"
the President directed the Secretary of Defense to take Padilla into
military custody, in which custody Padilla has remained ever since.
The full text of the President’s memorandum to the Secretary of
Defense reads as follows:
                           PADILLA v. HANFT                             5
                        THE WHITE HOUSE
                              WASHINGTON

                    FOR OFFICIAL USE ONLY

TO THE SECRETARY OF DEFENSE:

Based on the information available to me from all sources,

                             REDACTED

In accordance with the Constitution and consistent with the laws of
the United States, including the Authorization for Use of Military
Force Joint Resolution (Public Law 107-40);

I, GEORGE W. BUSH, as President of the United States and Com-
mander in Chief of the U.S. armed forces, hereby DETERMINE for
the United States of America that:

   (1) Jose Padilla, who is under the control of the Department of Jus-
tice and who is a U.S. citizen, is, and at the time he entered the United
States in May 2002 was, an enemy combatant;

   (2) Mr. Padilla is closely associated with al Qaeda, an international
terrorist organization with which the United States is at war;

   (3) Mr. Padilla engaged in conduct that constituted hostile and war-
like acts, including conduct in preparation for acts of international ter-
rorism that had the aim to cause injury to or adverse effects on the
United States;

   (4) Mr. Padilla possesses intelligence, including intelligence about
personnel and activities of al Qaeda, that, if communicated to the
U.S., would aid U.S. efforts to prevent attacks by al Qaeda on the
United States or its armed forces, other governmental personnel, or
citizens;

   (5) Mr. Padilla represents a continuing, present and grave danger
to the national security of the United States, and detention of Mr.
6                          PADILLA v. HANFT
Padilla is necessary to prevent him from aiding al Qaeda in its efforts
to attack the United States or its armed forces, other governmental
personnel, or citizens;

  (6) it is in the interest of the United States that the Secretary of
Defense detain Mr. Padilla as an enemy combatant; and

  (7) it is REDACTED consistent with U.S. law and the laws of
war for the Secretary of Defense to detain Mr. Padilla as enemy com-
batant.

Accordingly, you are directed to receive Mr. Padilla from the Depart-
ment of Justice and to detain him as an enemy combatant.

DATE: June 9, 2002                           Signature
                                             /George Bush/

   The exceedingly important question before us is whether the Presi-
dent of the United States possesses the authority to detain militarily
a citizen of this country who is closely associated with al Qaeda, an
entity with which the United States is at war; who took up arms on
behalf of that enemy and against our country in a foreign combat zone
of that war; and who thereafter traveled to the United States for the
avowed purpose of further prosecuting that war on American soil,
against American citizens and targets.

  We conclude that the President does possess such authority pursu-
ant to the Authorization for Use of Military Force Joint Resolution
enacted by Congress in the wake of the attacks on the United States
of September 11, 2001. Accordingly, the judgment of the district
court is reversed.

                                    I.

   Al Qaeda operatives recruited Jose Padilla, a United States citizen,
to train for jihad in Afghanistan in February 2000, while Padilla was
on a religious pilgrimage to Saudi Arabia.1 J.A. 18-19. Subsequently,
    1
    For purposes of Padilla’s summary judgment motion, the parties have
stipulated to the facts as set forth by the government. J.A. 30-31. It is
only on these facts that we consider whether the President has the author-
ity to detain Padilla.
                           PADILLA v. HANFT                           7
Padilla met with al Qaeda operatives in Afghanistan, received explo-
sives training in an al Qaeda-affiliated camp, and served as an armed
guard at what he understood to be a Taliban outpost. Id. at 19-20.
When United States military operations began in Afghanistan, Padilla
and other al Qaeda operatives moved from safehouse to safehouse to
evade bombing or capture. Id. at 20. Padilla was, on the facts with
which we are presented, "armed and present in a combat zone during
armed conflict between al Qaeda/Taliban forces and the armed forces
of the United States." Id. at 21.

   Padilla eventually escaped to Pakistan, armed with an assault rifle.
Id. at 20-21. Once in Pakistan, Padilla met with Khalid Sheikh
Mohammad, a senior al Qaeda operations planner, who directed
Padilla to travel to the United States for the purpose of blowing up
apartment buildings, in continued prosecution of al Qaeda’s war of
terror against the United States. See id. at 22. After receiving further
training, as well as cash, travel documents, and communication
devices, Padilla flew to the United States in order to carry out his
accepted assignment. Id. at 22-23.

   Upon arrival at Chicago’s O’Hare International Airport on May 8,
2002, Padilla was detained by FBI agents, who interviewed and even-
tually arrested him pursuant to a material witness warrant issued by
the district court for the Southern District of New York in conjunction
with a grand jury investigation of the September 11 attacks. Id. at 93.
Padilla was transported to New York, where he was held at a civilian
correctional facility until, on June 9, 2002, the President designated
him an "enemy combatant" against the United States and directed the
Secretary of Defense to take him into military custody. Id. at 16, 94.
Since his delivery into the custody of military authorities, Padilla has
been detained at a naval brig in South Carolina. Id. at 162-63.

   On June 11, 2002, Padilla filed a petition for a writ of habeas cor-
pus in the Southern District of New York, claiming that his detention
violated the Constitution. Id. at 164. The Supreme Court of the United
States ultimately ordered Padilla’s petition dismissed without preju-
dice, holding that his petition was improperly filed in the Southern
District of New York. Rumsfeld v. Padilla, 124 S. Ct. 2711, 2727
(2004). And on July 2, 2004, Padilla filed the present petition for a
writ of habeas corpus in the District of South Carolina. J.A. 166.
8                            PADILLA v. HANFT
   The district court subsequently held that the President lacks the
authority to detain Padilla, id. at 180-81, that Padilla’s detention is in
violation of the Constitution and laws of the United States, id., and
that Padilla therefore must either be criminally charged or released,
id. at 183. This appeal followed. We expedited consideration of this
appeal at the request of the parties, hearing argument in the case on
July 19, 2005.

                                     II.

                                     A.

  The Authorization for Use of Military Force Joint Resolution
(AUMF), upon which the President explicitly relied in his order that
Padilla be detained by the military and upon which the government
chiefly relies in support of the President’s authority to detain Padilla,
was enacted by Congress in the immediate aftermath of the Septem-
ber 11, 2001, terrorist attacks on the United States. It provides as fol-
lows:

        [T]he President is authorized to use all necessary and appro-
        priate force against those nations, organizations, or persons
        he determines planned, authorized, committed, or aided the
        terrorist attacks that occurred on September 11, 2001, or
        harbored such organizations or persons, in order to prevent
        any future acts of international terrorism against the United
        States by such nations, organizations or persons.

Pub. L. No. 107-40, § 2(a), 115 Stat. 224 (September 18, 2001). The
Supreme Court has already once interpreted this Joint Resolution in
the context of a military detention by the President. In Hamdi v.
Rumsfeld, 124 S. Ct. 2633 (2004), the Supreme Court held, on the
facts alleged by the government, that the AUMF authorized the mili-
tary detention of Yaser Esam Hamdi, an American citizen who fought
alongside Taliban forces in Afghanistan, was captured by United
States allies on a battlefield there, and was detained in the United
States by the military.2 Id. at 2635-37, 2641. The "narrow question,"
    2
   Having concluded that detention was authorized on the facts alleged
by the government, the Court in Hamdi remanded the case for a hearing
to determine, pursuant to the due process requirements set forth in its
opinion, whether those alleged facts were true. Hamdi, 124 S. Ct. at
2635, 2648-52.
                           PADILLA v. HANFT                           9
id. at 2639, addressed by the Court in Hamdi was "whether the Exec-
utive has the authority to detain citizens who qualify as ‘enemy com-
batants,’" id., defined for purposes of that case as "individual[s] who
. . . [were] ‘"part of or supporting forces hostile to the United States
or coalition partners"’ in Afghanistan and who ‘"engaged in an armed
conflict against the United States"’ there," id. The controlling plural-
ity of the Court answered that narrow question in the affirmative, con-
cluding, based upon "longstanding law-of-war principles," id. at 2641,
that Hamdi’s detention was "necessary and appropriate" within the
meaning of the AUMF because "[t]he capture and detention of lawful
combatants and the capture, detention, and trial of unlawful comba-
tants, by ‘universal agreement and practice,’ are ‘important inci-
dent[s] of war,’" id. at 2640 (quoting Ex parte Quirin, 317 U.S. 1, 28
(1942)). The rationale for this law-of-war principle, Justice O’Connor
explained for the plurality, is that "detention to prevent a combatant’s
return to the battlefield is a fundamental incident of waging war." Id.
at 2641.

   As the AUMF authorized Hamdi’s detention by the President, so
also does it authorize Padilla’s detention. Under the facts as presented
here, Padilla unquestionably qualifies as an "enemy combatant" as
that term was defined for purposes of the controlling opinion in
Hamdi. Indeed, under the definition of "enemy combatant" employed
in Hamdi, we can discern no difference in principle between Hamdi
and Padilla. Like Hamdi, Padilla associated with forces hostile to the
United States in Afghanistan. Compare J.A. 19-23 (detailing Padilla’s
association with al Qaeda in Afghanistan and Pakistan), with Hamdi,
124 S. Ct. at 2637 (describing Hamdi’s affiliation with the Taliban in
Afghanistan). And, like Hamdi, Padilla took up arms against United
States forces in that country in the same way and to the same extent
as did Hamdi. Compare J.A. 21 (averring that Padilla was "armed and
present in a combat zone during armed conflict between al
Qaeda/Taliban forces and the armed forces of the United States"), and
id. at 20-21 (alleging that Padilla was "armed with an assault rifle" as
he escaped to Pakistan), with Hamdi, 124 S. Ct. at 2642 n.1 (noting
that the asserted basis for detaining Hamdi was that he "carr[ied] a
weapon against American troops on a foreign battlefield"), and id. at
2637 (quoting Mobbs Affidavit that Hamdi had "‘surrender[ed] his
Kalishnikov assault rifle’" to Northern Alliance forces (alteration in
original)). Because, like Hamdi, Padilla is an enemy combatant, and
10                         PADILLA v. HANFT
because his detention is no less necessary than was Hamdi’s in order
to prevent his return to the battlefield, the President is authorized by
the AUMF to detain Padilla as a fundamental incident to the conduct
of war.

   Our conclusion that the AUMF as interpreted by the Supreme
Court in Hamdi authorizes the President’s detention of Padilla as an
enemy combatant is reinforced by the Supreme Court’s decision in Ex
parte Quirin, 317 U.S. 1 (1942), on which the plurality in Hamdi
itself heavily relied. In Quirin, the Court held that Congress had
authorized the military trial of Haupt, a United States citizen who
entered the country with orders from the Nazis to blow up domestic
war facilities but was captured before he could execute those orders.
Id. at 20-21, 28, 46. The Court reasoned that Haupt’s citizenship was
no bar to his military trial as an unlawful enemy belligerent, conclud-
ing that "[c]itizens who associate themselves with the military arm of
the enemy government, and with its aid, guidance and direction enter
this country bent on hostile acts, are enemy belligerents within the
meaning of . . . the law of war." Id. at 37-38.

   Like Haupt, Padilla associated with the military arm of the enemy,
and with its aid, guidance, and direction entered this country bent on
committing hostile acts on American soil. J.A. 22-23. Padilla thus
falls within Quirin’s definition of enemy belligerent, as well as within
the definition of the equivalent term accepted by the plurality in
Hamdi. Compare Quirin, 317 U.S. at 37-38 (holding that "[c]itizens
who associate themselves with the military arm of the enemy govern-
ment, and with its aid, guidance and direction enter this country bent
on hostile acts, are enemy belligerents within the meaning of . . . the
law of war"), with Hamdi, 124 S. Ct. at 2639 (accepting for purposes
of the case the government’s definition of "enemy combatants" as
those who were "‘"part of or supporting forces hostile to the United
States or coalition partners"’ in Afghanistan and who ‘"engaged in an
armed conflict against the United States"’ there").

   We understand the plurality’s reasoning in Hamdi to be that the
AUMF authorizes the President to detain all those who qualify as
"enemy combatants" within the meaning of the laws of war, such
power being universally accepted under the laws of war as necessary
in order to prevent the return of combatants to the battlefield during
                            PADILLA v. HANFT                            11
conflict. Id. at 2640-41. Given that Padilla qualifies as an enemy com-
batant under both the definition adopted by the Court in Quirin and
the definition accepted by the controlling opinion in Hamdi, his mili-
tary detention as an enemy combatant by the President is unquestion-
ably authorized by the AUMF as a fundamental incident to the
President’s prosecution of the war against al Qaeda in Afghanistan.3

                                    B.

   Padilla marshals essentially four arguments for the conclusion that
his detention is unlawful. None of them ultimately is persuasive.

                                    1.

   Recognizing the hurdle to his position represented by the Supreme
Court’s decision in Hamdi, Padilla principally argues that his case
does not fall within the "narrow circumstances" considered by the
Court in that case because, although he too stood alongside Taliban
forces in Afghanistan, he was seized on American soil, whereas
Hamdi was captured on a foreign battlefield. In other words, Padilla
maintains that capture on a foreign battlefield was one of the "narrow
circumstances" to which the plurality in Hamdi confined its opinion.
We disagree. When the plurality articulated the "narrow question"
before it, it referred simply to the permissibility of detaining "an indi-
vidual who . . . was ‘"part of or supporting forces hostile to the United
States or coalition partners"’ in Afghanistan and who ‘"engaged in an
armed conflict against the United States"’ there." Id. at 2639.
Nowhere in its framing of the "narrow question" presented did the
plurality even mention the locus of capture.

   The actual reasoning that the plurality thereafter employed is con-
sistent with the question having been framed so as to render locus of
capture irrelevant. That reasoning was that Hamdi’s detention was an
  3
    Under Hamdi, the power to detain that is authorized under the AUMF
is not a power to detain indefinitely. Detention is limited to the duration
of the hostilities as to which the detention is authorized. 124 S. Ct. at
2641-42. Because the United States remains engaged in the conflict with
al Qaeda in Afghanistan, Padilla’s detention has not exceeded in duration
that authorized by the AUMF.
12                         PADILLA v. HANFT
exercise of "necessary and appropriate force" within the meaning of
the AUMF because "detention to prevent a combatant’s return to the
battlefield is a fundamental incident of waging war." Id. at 2641. This
reasoning simply does not admit of a distinction between an enemy
combatant captured abroad and detained in the United States, such as
Hamdi, and an enemy combatant who escaped capture abroad but was
ultimately captured domestically and detained in the United States,
such as Padilla. As we previously explained, Padilla poses the same
threat of returning to the battlefield as Hamdi posed at the time of the
Supreme Court’s adjudication of Hamdi’s petition. Padilla’s detention
is thus "necessary and appropriate" to the same extent as was
Hamdi’s.

   Padilla directs us to a passage from the plurality’s opinion in
Hamdi in which, when responding to the dissent, the plurality charged
that the dissent "ignore[d] the context of th[e] case: a United States
citizen captured in a foreign combat zone." Id. at 2643. Padilla argues
that this passage proves that capture on a foreign battlefield was one
of the factual circumstances by which the Court’s opinion was lim-
ited. If this language stood alone, Padilla’s argument as to the limita-
tion of Hamdi at least would have more force, though to acknowledge
that foreign battlefield capture was part of the context of the case still
is not to say (at least not necessarily) that the locus of capture was
essential to the Court’s reasoning. However, this language simply
cannot bear the weight that Padilla would have it bear when it is con-
sidered against the backdrop of both the quite different limitations
that were expressly imposed by the Court through its framing of the
question presented, and the actual reasoning that was employed by the
Court in reaching its conclusion, which reasoning was consistent with
the question having been framed so as to render an enemy comba-
tant’s point of capture irrelevant to the President’s power to detain.
In short, the plurality carefully limited its opinion, but not in a way
that leaves room for argument that the President’s power to detain one
who has associated with the enemy and taken up arms against the
United States in a foreign combat zone varies depending upon the
geographic location where that enemy combatant happens to be cap-
tured.

   Our conclusion that the reasoning in Hamdi does not support a dis-
tinction based on the locus of capture is buttressed by the plurality’s
                            PADILLA v. HANFT                             13
analysis of Quirin. Although at issue in Quirin was the authority of
the President to subject a United States citizen who was also an
enemy combatant to military trial, the plurality in Hamdi went to
lengths to observe that Haupt, who had been captured domestically,
could instead have been permissibly detained for the duration of hos-
tilities. See id. at 2640. That analysis strongly suggests, if it does not
confirm, that the plurality did not regard the locus of capture (within
or without the United States) as relevant to the President’s authority
to detain an enemy combatant who is also a citizen, and that it
believed that the detention of such a combatant is not more or less a
necessary incident of the President’s power to wage war depending
upon the locus of eventual capture.

   Given the lack of any reference to locus of capture in the plurality’s
articulation of the "narrow question" before it, the absence of any
basis in Hamdi’s reasoning for a distinction between foreign and
domestic capture of one who has both associated with the enemy and
taken up arms against the United States on behalf of that enemy in a
foreign combat zone, and the plurality’s understanding of and reliance
upon Quirin as a precedent that would permit the detention of an
enemy combatant who had been captured domestically, we simply
cannot ascribe to the rejoinder to Justice Scalia the significance, much
less the dispositive significance, that Padilla urges.4

                                     2.

   Padilla also argues, and the district court held, that Padilla’s mili-
tary detention is "neither necessary nor appropriate" because he is
amenable to criminal prosecution. J.A. 172. Related to this argument,
Padilla attempts to distinguish Quirin from his case on the grounds
  4
    Padilla also argues that the locus of capture should be legally relevant
to the scope of the AUMF’s authorization because there is a higher prob-
ability of an erroneous determination that one is an enemy combatant
when the seizure occurs on American soil. It is far from clear that this
is actually the case. In any event, Padilla’s argument confuses the scope
of the President’s power to detain enemy combatants under the AUMF
with the process for establishing that a detainee is in fact an enemy com-
batant. Hamdi itself provides process to guard against the erroneous
detention of non-enemy combatants. 124 S. Ct. at 2648-52.
14                         PADILLA v. HANFT
that he has simply been detained, unlike Haupt who was charged and
tried in Quirin. Neither the argument nor the attempted distinction is
convincing.

   As to the fact that Padilla can be prosecuted, the availability of
criminal process does not distinguish him from Hamdi. If the mere
availability of criminal prosecution rendered detention unnecessary
within the meaning of the AUMF, then Hamdi’s detention would
have been unnecessary and therefore unauthorized, since he too was
detained in the United States and amenable to criminal prosecution.
We are convinced, in any event, that the availability of criminal pro-
cess cannot be determinative of the power to detain, if for no other
reason than that criminal prosecution may well not achieve the very
purpose for which detention is authorized in the first place — the pre-
vention of return to the field of battle. Equally important, in many
instances criminal prosecution would impede the Executive in its
efforts to gather intelligence from the detainee and to restrict the
detainee’s communication with confederates so as to ensure that the
detainee does not pose a continuing threat to national security even
as he is confined — impediments that would render military detention
not only an appropriate, but also the necessary, course of action to be
taken in the interest of national security.

   The district court acknowledged the need to defer to the President’s
determination that Padilla’s detention is necessary and appropriate in
the interest of national security. See id. at 179. However, we believe
that the district court ultimately accorded insufficient deference to
that determination, effectively imposing upon the President the equiv-
alent of a least-restrictive-means test. To subject to such exacting
scrutiny the President’s determination that criminal prosecution
would not adequately protect the Nation’s security at a very minimum
fails to accord the President the deference that is his when he acts pur-
suant to a broad delegation of authority from Congress, such as the
AUMF.

   As for Padilla’s attempted distinction of Quirin on the grounds
that, unlike Haupt, he has never been charged and tried by the mili-
tary, the plurality in Hamdi rejected as immaterial the distinction
between detention and trial (apparently regarding the former as a
lesser imposition than the latter), noting that "nothing in Quirin sug-
                           PADILLA v. HANFT                            15
gests that [Haupt’s United States] citizenship would have precluded
his mere detention for the duration of the relevant hostilities." Hamdi,
124 S. Ct. at 2640 (emphasis added).

                                    3.

  Padilla, citing Ex parte Endo, 323 U.S. 283 (1944), and relying
upon Quirin, next argues that only a clear statement from Congress
can authorize his detention, and that the AUMF is not itself, and does
not contain, such a clear statement.

   In Endo, the Court did state that, when asked to find implied pow-
ers in a wartime statute, it must assume that "the law makers intended
to place no greater restraint on the citizen than was clearly and unmis-
takably indicated by the language [the law makers] used." Id. at 300.
The Court almost immediately thereafter observed, however, that the
"fact that the Act" at issue was "silent on detention [did] not of course
mean that any power to detain [was] lacking," id. at 301, an observa-
tion that proves that the Court did not adopt or even apply in that case
a "clear statement" rule of the kind for which Padilla argues.5

   Padilla contends that Quirin also supports the existence of a clear
statement rule. However, in no place in Quirin did the Court even
purport to establish a clear statement rule. In its opinion, the Court did
note that Congress had "explicitly" authorized Haupt’s military trial.
See 317 U.S. at 28. But to conclude from this passing note that the
Court required a clear statement as a matter of law would be unwar-
ranted. In fact, to the extent that Quirin can be understood to have
addressed the need for a clear statement of authority from Congress
at all, the rule would appear the opposite:
  5
    At issue in Endo was the detention of a "concededly loyal" citizen,
not an enemy combatant. 323 U.S. at 302. In the face of the statute’s
silence on detention, the Court looked to the statute’s purpose — the pre-
vention of espionage and sabotage — to determine whether Endo’s
detention was authorized. See id. at 300-02. The Court concluded that it
was not, because detention of a concededly loyal citizen bore no relation
to the prevention of espionage and sabotage. Id. at 302. Padilla’s deten-
tion, by contrast, emphatically does further the purpose of the AUMF —
"to prevent any future acts of international terrorism against the United
States," Pub. L. No. 107-40, § 2(a), 115 Stat. 224 (2001).
16                         PADILLA v. HANFT
     [T]he detention and trial of petitioners — ordered by the
     President in the declared exercise of his powers as Com-
     mander in Chief of the Army in time of war and of grave
     public danger — are not to be set aside by the courts without
     the clear conviction that they are in conflict with the Consti-
     tution or laws of Congress constitutionally enacted.

Id. at 25.

   Of course, even were a clear statement by Congress required, the
AUMF constitutes such a clear statement according to the Supreme
Court. In Hamdi, stating that "it [was] of no moment that the AUMF
does not use specific language of detention," 124 S. Ct. at 2641, the
plurality held that the AUMF "clearly and unmistakably authorized"
Hamdi’s detention, id. Nothing in the AUMF permits us to conclude
that the Joint Resolution clearly and unmistakably authorized
Hamdi’s detention but not Padilla’s. To the contrary, read in light of
its purpose clause ("in order to prevent any future acts of international
terrorism against the United States") and its preamble (stating that the
acts of 9/11 "render it both necessary and appropriate . . . to protect
United States citizens both at home and abroad"), the AUMF applies
even more clearly and unmistakably to Padilla than to Hamdi. Padilla,
after all, in addition to supporting hostile forces in Afghanistan and
taking up arms against our troops on a battlefield in that country like
Hamdi, also came to the United States in order to commit future acts
of terrorism against American citizens and targets.

   These facts unquestionably establish that Padilla poses the requisite
threat of return to battle in the ongoing armed conflict between the
United States and al Qaeda in Afghanistan, and that his detention is
authorized as a "fundamental incident of waging war," id., in order "to
prevent a combatant’s return to the battlefield," id. Congress "clearly
and unmistakably," id., authorized such detention when, in the
AUMF, it "permitt[ed] the use of ‘necessary and appropriate force,’"
id., to prevent other attacks like those of September 11, 2001.

                                   4.

   Finally, Padilla argues that, even if his detention is authorized by
the AUMF, it is unlawful under Ex parte Milligan, 71 U.S. (4 Wall.)
                           PADILLA v. HANFT                            17
2 (1866). In Milligan, the Supreme Court held that a United States cit-
izen associated with an anti-Union secret society but unaffiliated with
the Confederate army could not be tried by a military tribunal while
access to civilian courts was open and unobstructed. Id. at 6-7, 121.
Milligan purported to restrict the power of Congress as well as the
power of the President. Id. at 121-22 ("[N]o usage of war could sanc-
tion a military trial . . . for any offence whatever of a citizen in civil
life, in nowise connected with the military service. Congress could
grant no such power . . ."). Quirin, however, confirmed that Milligan
does not extend to enemy combatants. As the Court in Quirin
explained, the Milligan Court’s reasoning had "particular reference to
the facts before it," namely, that Milligan was not "a part of or associ-
ated with the armed forces of the enemy." See 317 U.S. at 45. The
Hamdi plurality in turn reaffirmed this limitation on the reach of Mil-
ligan, emphasizing that Quirin, a unanimous opinion, "both postdates
and clarifies Milligan." 124 S. Ct. at 2643. Thus confined, Milligan
is inapposite here because Padilla, unlike Milligan, associated with,
and has taken up arms against the forces of the United States on
behalf of, an enemy of the United States.

                                   III.

   The Congress of the United States, in the Authorization for Use of
Military Force Joint Resolution, provided the President all powers
necessary and appropriate to protect American citizens from terrorist
acts by those who attacked the United States on September 11, 2001.
As would be expected, and as the Supreme Court has held, those pow-
ers include the power to detain identified and committed enemies
such as Padilla, who associated with al Qaeda and the Taliban regime,
who took up arms against this Nation in its war against these enemies,
and who entered the United States for the avowed purpose of further
prosecuting that war by attacking American citizens and targets on
our own soil — a power without which, Congress understood, the
President could well be unable to protect American citizens from the
very kind of savage attack that occurred four years ago almost to the
day.

  The detention of petitioner being fully authorized by Act of Con-
gress, the judgment of the district court that the detention of petitioner
18                      PADILLA v. HANFT
by the President of the United States is without support in law is
hereby reversed.

                                                      REVERSED
