(Slip Opinion)              OCTOBER TERM, 2014                                       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

        DEPARTMENT OF HOMELAND SECURITY v. 

                    MACLEAN 


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

  No. 13–894.      Argued November 4, 2014—Decided January 21, 2015
In 2002, Congress enacted the Homeland Security Act, 116 Stat. 2135.
  That Act provides that the Transportation Security Administration
  (TSA) “shall prescribe regulations prohibiting the disclosure of infor-
  mation . . . if the Under Secretary decides that disclosur[e] would . . .
  be detrimental to the security of transportation.”         49 U. S. C.
  §114(r)(1)(C). Around the same time, the TSA promulgated regula-
  tions prohibiting the unauthorized disclosure of “sensitive security in-
  formation,” 67 Fed. Reg. 8351, which included “[s]pecific details of
  aviation security measures . . . [such as] information concerning spe-
  cific numbers of Federal Air Marshals, deployments or missions, and
  the methods involved in such operations,” 49 CFR §1520.7(j).
     In July 2003, the TSA briefed all federal air marshals—including
  Robert J. MacLean—about a potential plot to hijack passenger
  flights. A few days after the briefing, MacLean received from the
  TSA a text message cancelling all overnight missions from Las Vegas
  until early August. MacLean, who was stationed in Las Vegas, be-
  lieved that cancelling those missions during a hijacking alert was
  dangerous and illegal. He therefore contacted a reporter and told
  him about the TSA’s decision to cancel the missions. After discover-
  ing that MacLean was the source of the disclosure, the TSA fired him
  for disclosing sensitive security information without authorization.
     MacLean challenged his firing before the Merit Systems Protection
  Board. He argued that his disclosure was whistleblowing activity
  under 5 U. S. C. §2302(b)(8)(A), which protects employees who dis-
  close information that reveals “any violation of any law, rule, or regu-
  lation,” or “a substantial and specific danger to public health or safe-
  ty.” The Board held that MacLean did not qualify for protection
2      DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                                 Syllabus

    under that statute because his disclosure was “specifically prohibited
    by law,” §2302(b)(8)(A)—namely, by 49 U. S. C. §114(r)(1). The Court
    of Appeals for the Federal Circuit vacated the Board’s decision, hold-
    ing that Section 114(r)(1) was not a prohibition.
Held: MacLean’s disclosure was not “specifically prohibited by law.”
 Pp. 5–16.
    (a) The Government argues that MacLean’s disclosure was “specifi-
 cally prohibited by law” in two ways: first, by the TSA’s regulations
 on sensitive security information, and second, by Section 114(r)(1) it-
 self, which authorized the TSA to promulgate those regulations.
 Pp. 5–14.
      (i) MacLean’s disclosure was not prohibited by the TSA’s regula-
 tions for purposes of Section 2302(b)(8)(A) because regulations do not
 qualify as “law” under that statute. Throughout Section 2302, Con-
 gress repeatedly used the phrase “law, rule, or regulation.” But Con-
 gress did not use that phrase in the statutory language at issue here;
 it used the word “law” standing alone. Congress’s choice to say “spe-
 cifically prohibited by law,” instead of “specifically prohibited by law,
 rule, or regulation” suggests that Congress meant to exclude rules
 and regulations. In addition, Section 2302(b)(8)(A) creates a second
 exception for disclosures “required by Executive order to be kept se-
 cret in the interest of national defense or the conduct of foreign af-
 fairs.” That the second exception is limited to actions by the Presi-
 dent himself suggests that the first exception does not include action
 taken by executive agencies. Finally, interpreting the word “law” to
 include rules and regulations could defeat the purpose of the whistle-
 blower statute. That interpretation would allow an agency to insu-
 late itself from Section 2302(b)(8)(A) simply by promulgating a regu-
 lation that “specifically prohibited” all whistleblowing.
    The Government proposes two alternative interpretations, but nei-
 ther is persuasive. First, the Government argues that the word “law”
 includes all regulations that have the “force and effect of law.” The
 Government bases this argument on the decision in Chrysler Corp. v.
 Brown, 441 U. S. 281, where this Court held that legislative regula-
 tions generally fall within the meaning of the word “law” unless there
 is a “clear showing of contrary legislative intent.” Id., at 295–296.
 But Congress’s use of the word “law,” in close connection with the
 phrase “law, rule, or regulation,” provides the necessary “clear show-
 ing” that “law” does not include regulations in this case. Second, the
 Government argues that the word “law” includes at least those regu-
 lations that were “promulgated pursuant to an express congressional
 directive.” The Government, however, was unable to find a single ex-
 ample of the word “law” being used in that way. Pp. 6–11.
      (ii) Likewise, MacLean’s disclosure was not prohibited by Section
                     Cite as: 574 U. S. ____ (2015)                    3

                                Syllabus

  114(r)(1). That statute does not prohibit anything; instead, it author-
  izes the TSA to “prescribe regulations.” Thus, by its terms, Section
  114(r)(1) did not prohibit the disclosure here. The Government re-
  sponds that Section 114(r)(1) did prohibit MacLean’s disclosure by
  imposing a “legislative mandate” on the TSA to promulgate regula-
  tions to that effect. But the statute affords substantial discretion to
  the TSA in deciding whether to prohibit any particular disclosure.
  Thus, it is the TSA’s regulations—not the statute—that prohibited
  MacLean’s disclosure, and those regulations do not qualify as “law”
  under Section 2302(b)(8)(A). Pp. 11–14.
     (b) The Government argues that providing whistleblower protec-
  tion to individuals like MacLean would “gravely endanger public
  safety” by making the confidentiality of sensitive security infor-
  mation depend on the idiosyncratic judgment of each of the TSA’s
  60,000 employees. Those concerns are legitimate, but they must be
  addressed by Congress or the President, rather than by this Court.
  Pp. 14–15.
714 F. 3d. 1301, affirmed.

  ROBERTS, C. J., delivered the opinion of the Court, in which SCALIA,
THOMAS, GINSBURG, BREYER, ALITO, and KAGAN, JJ., joined. SO-
TOMAYOR, J., filed a dissenting opinion, in which KENNEDY, J., joined.
                        Cite as: 574 U. S. ____ (2015)                              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. 13–894
                                   _________________


      DEPARTMENT OF HOMELAND SECURITY, 

        PETITIONER v. ROBERT J. MACLEAN 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FEDERAL CIRCUIT

                               [January 21, 2015]


   CHIEF JUSTICE ROBERTS delivered the opinion of the
Court.
   Federal law generally provides whistleblower protec-
tions to an employee who discloses information revealing
“any violation of any law, rule, or regulation,” or “a sub-
stantial and specific danger to public health or safety.” 5
U. S. C. §2302(b)(8)(A). An exception exists, however, for
disclosures that are “specifically prohibited by law.” Ibid.
Here, a federal air marshal publicly disclosed that the
Transportation Security Administration (TSA) had de-
cided to cut costs by removing air marshals from certain
long-distance flights. The question presented is whether
that disclosure was “specifically prohibited by law.”
                              I

                             A

  In 2002, Congress enacted the Homeland Security Act,
116 Stat. 2135. As relevant here, that Act provides that
the TSA “shall prescribe regulations prohibiting the dis-
closure of information obtained or developed in carrying
out security . . . if the Under Secretary decides that dis-
closing the information would . . . be detrimental to the
2    DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                      Opinion of the Court

security of transportation.” 49 U. S. C. §114(r)(1)(C).
   Around the same time, the TSA promulgated regula-
tions prohibiting the unauthorized disclosure of what it
called “sensitive security information.” See 67 Fed. Reg.
8351 (2002). The regulations described 18 categories of
sensitive security information, including “[s]pecific details
of aviation security measures . . . [such as] information
concerning specific numbers of Federal Air Marshals,
deployments or missions, and the methods involved in
such operations.” 49 CFR §1520.7(j) (2002). Sensitive
security information is not classified, so the TSA can share
it with individuals who do not have a security clearance,
such as airport employees. Compare Exec. Order 13526,
§4.1, 3 CFR 298, 314–315 (2009 Comp.), with 49 CFR
§1520.11(c) (2013).
                                B
  Robert J. MacLean became a federal air marshal for the
TSA in 2001. In that role, MacLean was assigned to pro-
tect passenger flights from potential hijackings. See 49
U. S. C. §44917(a).
  On July 26, 2003, the Department of Homeland Security
(DHS) issued a confidential advisory about a potential
hijacking plot. The advisory said that members of the
terrorist group al Qaeda were planning to attack passen-
ger flights, and that they “considered suicide hijackings
and bombings as the most promising methods to destroy
aircraft in flight, as well as to strike ground targets.” App.
16. The advisory identified a number of potential targets,
including the United Kingdom, Italy, Australia, and the
east coast of the United States. Finally, the advisory
warned that at least one of the attacks “could be executed
by the end of the summer 2003.” Ibid.
  The TSA soon summoned all air marshals (including
MacLean) for face-to-face briefings about the hijacking
plot. During MacLean’s briefing, a TSA official told him
                 Cite as: 574 U. S. ____ (2015)            3

                     Opinion of the Court

that the hijackers were planning to “smuggle weapons in
camera equipment or children’s toys through foreign
security,” and then “fly into the United States . . . into an
airport that didn’t require them to be screened.” Id., at 92.
The hijackers would then board U. S. flights, “overpower
the crew or the Air Marshals and . . . fly the planes into
East Coast targets.” Id., at 93.
   A few days after the briefing, MacLean received from
the TSA a text message cancelling all overnight missions
from Las Vegas until early August. MacLean, who was
stationed in Las Vegas, believed that cancelling those
missions during a hijacking alert was dangerous. He also
believed that the cancellations were illegal, given that
federal law required the TSA to put an air marshal on
every flight that “present[s] high security risks,” 49
U. S. C. §44917(a)(2), and provided that “nonstop, long
distance flights, such as those targeted on September 11,
2001, should be a priority,” §44917(b). See App. 95, 99,
101.
   MacLean therefore asked a supervisor why the TSA had
canceled the missions. The supervisor responded that the
TSA wanted “to save money on hotel costs because there
was no more money in the budget.” Id., at 95. MacLean
also called the DHS Inspector General’s Office to report
the cancellations. But a special agent in that office told
him there was “nothing that could be done.” Id., at 97.
   Unwilling to accept those responses, MacLean contacted
an MSNBC reporter and told him about the canceled
missions. In turn, the reporter published a story about
the TSA’s decision, titled “Air Marshals pulled from key
flights.” Id., at 36. The story reported that air marshals
would “no longer be covering cross-country or international
flights” because the agency did not want them “to incur
the expense of staying overnight in hotels.” Ibid. The
story also reported that the cancellations were “particularly
disturbing to some” because they “coincide[d] with a
4     DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                          Opinion of the Court

new high-level hijacking threat issued by the Department
of Homeland Security.” Id., at 37.
   After MSNBC published the story, several Members of
Congress criticized the cancellations. Within 24 hours, the
TSA reversed its decision and put air marshals back on
the flights. Id., at 50.
   At first, the TSA did not know that MacLean was the
source of the disclosure. In September 2004, however,
MacLean appeared on NBC Nightly News to criticize the
TSA’s dress code for air marshals, which he believed made
them too easy to identify. Although MacLean appeared in
disguise, several co-workers recognized his voice, and the
TSA began investigating the appearance. During that
investigation, MacLean admitted that he had disclosed the
text message back in 2003. Consequently, in April 2006,
the TSA fired MacLean for disclosing sensitive security
information without authorization.
   MacLean challenged his firing before the Merit Systems
Protection Board, arguing in relevant part that his disclo-
sure was protected whistleblowing activity under 5
U. S. C. §2302(b)(8)(A). The Board held that MacLean did
not qualify for protection under that statute, however,
because his disclosure was “specifically prohibited by law.”
116 MSPR 562, 569–572 (2011).
   The Court of Appeals for the Federal Circuit vacated the
Board’s decision. 714 F. 3d 1301 (2013). The parties had
agreed that, in order for MacLean’s disclosure to be “spe-
cifically prohibited by law,” it must have been “prohibited
by a statute rather than by a regulation.” Id., at 1308
(emphasis added). Thus, the issue before the court was
whether the statute authorizing the TSA’s regulations—
now codified at 49 U. S. C. §114(r)(1)—“specifically prohib-
ited” MacLean’s disclosure. 714 F. 3d, at 1308.*
——————
  * This statute has a complicated history. It was codified at 49 U. S. C.
§40119(b)(1) when the TSA initially promulgated its regulations on
                     Cite as: 574 U. S. ____ (2015)                   5

                         Opinion of the Court

   The court first held that Section 114(r)(1) was not a
prohibition. The statute did “not expressly prohibit em-
ployee disclosures,” the court explained, but instead em-
powered the TSA to “prescribe regulations prohibiting
disclosure[s]” if the TSA decided that disclosing the infor-
mation would harm public safety. Id., at 1309. The court
therefore concluded that MacLean’s disclosure was prohib-
ited by a regulation, which the parties had agreed could
not be a “law” under Section 2302(b)(8)(A). Ibid.
   The court then held that, even if Section 114(r)(1) were
a prohibition, it was not “sufficiently specific.” Ibid. The
court explained that a law is sufficiently specific only if it
“requires that matters be withheld from the public as to
leave no discretion on the issue, or . . . establishes particu-
lar criteria for withholding or refers to particular types of
matters to be withheld.” Ibid. (quoting S. Rep. No. 95–969
(1978)). And Section 114(r)(1) did not meet that test
because it “provide[d] only general criteria for withholding
information and [gave] some discretion to the [TSA] to
fashion regulations for prohibiting disclosure.” 714 F. 3d,
at 1309. The court accordingly vacated the Board’s deci-
sion and remanded for a determination of whether Mac-
Lean’s disclosure met the other requirements under Sec-
tion 2302(b)(8)(A). Id., at 1310–1311.
   We granted certiorari. 572 U. S. ___ (2014).
                            II
  Section 2302(b)(8) provides, in relevant part, that a
federal agency may not take
     “a personnel action with respect to any employee or
     applicant for employment because of
——————
sensitive security information. It was codified at §114(s)(1) when
MacLean disclosed the text message to MSNBC. And it is now codified
at §114(r)(1). The Federal Circuit referred to §40119(b)(1) in its opin-
ion. Because the statute has remained identical in all relevant re-
spects, however, we and the parties refer to the current version.
6    DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                      Opinion of the Court

    “(A) any disclosure of information by an employee or
    applicant which the employee or applicant reasonably
    believes evidences
    “(i) any violation of any law, rule, or regulation, or
    “(ii) gross mismanagement, a gross waste of funds, an
    abuse of authority, or a substantial and specific dan-
    ger to public health or safety,
    “if such disclosure is not specifically prohibited by law
    and if such information is not specifically required by
    Executive order to be kept secret in the interest of na-
    tional defense or the conduct of foreign affairs.”
   The Government argues that this whistleblower statute
does not protect MacLean because his disclosure regarding
the canceled missions was “specifically prohibited by law”
in two ways. First, the Government argues that the dis-
closure was specifically prohibited by the TSA’s regula-
tions on sensitive security information: 49 CFR
§§1520.5(a)–(b), 1520.7(j) (2003). Second, the Government
argues that the disclosure was specifically prohibited by
49 U. S. C. §114(r)(1), which authorized the TSA to pro-
mulgate those regulations. We address each argument in
turn.
                                A
                                 1
   In 2003, the TSA’s regulations prohibited the disclosure
of “[s]pecific details of aviation security measures . . . [such
as] information concerning specific numbers of Federal Air
Marshals, deployments or missions, and the methods
involved in such operations.” 49 CFR §1520.7(j). Mac-
Lean does not dispute before this Court that the TSA’s
regulations prohibited his disclosure regarding the can-
celed missions. Thus, the question here is whether a
disclosure that is specifically prohibited by regulation is
also “specifically prohibited by law” under Section
2302(b)(8)(A). (Emphasis added.)
                  Cite as: 574 U. S. ____ (2015)             7

                      Opinion of the Court

   The answer is no. Throughout Section 2302, Congress
repeatedly used the phrase “law, rule, or regulation.” For
example, Section 2302(b)(1)(E) prohibits a federal agency
from discriminating against an employee “on the basis of
marital status or political affiliation, as prohibited under
any law, rule, or regulation.” For another example, Sec-
tion 2302(b)(6) prohibits an agency from “grant[ing] any
preference or advantage not authorized by law, rule, or
regulation.” And for a third example, Section 2302(b)
(9)(A) prohibits an agency from retaliating against an
employee for “the exercise of any appeal, complaint, or
grievance right granted by any law, rule, or regulation.”
   In contrast, Congress did not use the phrase “law, rule,
or regulation” in the statutory language at issue here; it
used the word “law” standing alone. That is significant
because Congress generally acts intentionally when it uses
particular language in one section of a statute but omits it
in another. Russello v. United States, 464 U. S. 16, 23
(1983). Thus, Congress’s choice to say “specifically prohib-
ited by law” rather than “specifically prohibited by law,
rule, or regulation” suggests that Congress meant to ex-
clude rules and regulations.
   The interpretive canon that Congress acts intentionally
when it omits language included elsewhere applies with
particular force here for two reasons. First, Congress used
“law” and “law, rule, or regulation” in close proximity—
indeed, in the same sentence. §2302(b)(8)(A) (protecting
the disclosure of “any violation of any law, rule, or regula-
tion . . . if such disclosure is not specifically prohibited by
law”). Second, Congress used the broader phrase “law,
rule, or regulation” repeatedly—nine times in Section 2302
alone. See §§2302(a)(2)(D)(i), (b)(1)(E), (b)(6), (b)(8)(A)(i),
(b)(8)(B)(i), (b)(9)(A), (b)(12), (b)(13), (d)(5). Those two
aspects of the whistleblower statute make Con-
gress’s choice to use the narrower word “law” seem quite
deliberate.
8    DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                     Opinion of the Court

   We drew the same inference in Department of Treasury,
IRS v. FLRA, 494 U. S. 922 (1990). There, the Govern-
ment argued that the word “laws” in one section of the
Civil Service Reform Act of 1978 meant the same thing as
the phrase “law, rule, or regulation” in another section of
the Act. Id., at 931. We rejected that argument as “sim-
ply contrary to any reasonable interpretation of the text.”
Id., at 932. Indeed, we held that a statute that referred to
“laws” in one section and “law, rule, or regulation” in
another “cannot, unless we abandon all pretense at precise
communication, be deemed to mean the same thing in
both places.” Ibid. That inference is even more compel-
ling here, because the statute refers to “law” and “law,
rule, or regulation” in the same sentence, rather than
several sections apart.
   Another part of the statutory text points the same way.
After creating an exception for disclosures “specifically
prohibited by law,” Section 2302(b)(8)(A) goes on to create
a second exception for information “specifically required
by Executive order to be kept secret in the interest of
national defense or the conduct of foreign affairs.” This
exception is limited to action taken directly by the Presi-
dent. That suggests that the word “law” in the only other
exception is limited to actions by Congress—after all, it
would be unusual for the first exception to include action
taken by executive agencies, when the second exception
requires action by the President himself.
   In addition, a broad interpretation of the word “law”
could defeat the purpose of the whistleblower statute. If
“law” included agency rules and regulations, then an
agency could insulate itself from the scope of Section
2302(b)(8)(A) merely by promulgating a regulation that
“specifically prohibited” whistleblowing. But Congress
passed the whistleblower statute precisely because it did
not trust agencies to regulate whistleblowers within their
ranks. Thus, it is unlikely that Congress meant to include
                 Cite as: 574 U. S. ____ (2015)           9

                     Opinion of the Court

rules and regulations within the word “law.”
                               2
  The Government admits that some regulations fall
outside the word “law” as used in Section 2302(b)(8)(A).
But, the Government says, that does not mean that all
regulations are excluded. The Government suggests two
interpretations that would distinguish “law” from “law,
rule, or regulation,” but would still allow the word “law”
to subsume the TSA’s regulations on sensitive security
information.
  First, the Government argues that the word “law” in-
cludes all regulations that have the “force and effect of
law” (i.e., legislative regulations), while excluding those
that do not (e.g., interpretive rules). Brief for Petitioner
19–22. The Government bases this argument on our
decision in Chrysler Corp. v. Brown, 441 U. S. 281 (1979).
There, we held that legislative regulations generally fall
within the meaning of the word “law,” and that it would
take a “clear showing of contrary legislative intent” before
we concluded otherwise. Id., at 295–296. Thus, because
the TSA’s regulations have the force and effect of law, the
Government says that they should qualify as “law” under
the statute.
  The Government’s description of Chrysler is accurate
enough. But Congress’s use of the word “law,” in close
connection with the phrase “law, rule, or regulation,”
provides the necessary “clear showing” that “law” does not
include regulations. Indeed, using “law” and “law, rule, or
regulation” in the same sentence would be a very obscure
way of drawing the Government’s nuanced distinction
between different types of regulations. Had Congress
wanted to draw that distinction, there were far easier and
clearer ways to do so. For example, at the time Congress
passed Section 2302(b)(8)(A), another federal statute
defined the words “regulatory order” to include a “rule or
10   DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                      Opinion of the Court

regulation, if it has the force and effect of law.” 7 U. S. C.
§450c(a) (1976 ed.). Likewise, another federal statute
defined the words “State law” to include “all laws, deci-
sions, rules, regulations, or other State action having the
effect of law.” 29 U. S. C. §1144(c)(1) (1976 ed.). As those
examples show, Congress knew how to distinguish be-
tween regulations that had the force and effect of law and
those that did not, but chose not to do so in Section
2302(b)(8)(A).
   Second, the Government argues that the word “law”
includes at least those regulations that were “promulgated
pursuant to an express congressional directive.” Brief for
Petitioner 21. Outside of this case, however, the Govern-
ment was unable to find a single example of the word
“law” being used in that way. Not a single dictionary
definition, not a single statute, not a single case. The
Government’s interpretation happens to fit this case pre-
cisely, but it needs more than that to recommend it.
   Although the Government argues here that the word
“law” includes rules and regulations, it definitively re-
jected that argument in the Court of Appeals. For exam-
ple, the Government’s brief accepted that the word “law”
meant “legislative enactment,” and said that the “only
dispute” was whether 49 U. S. C. §114(r)(1) “serve[d] as
that legislative enactment.” Brief for Respondent in No.
11–3231 (CA Fed.), pp. 46–47. Then, at oral argument, a
judge asked the Government’s attorney the following
question: “I thought I understood your brief to concede
that [the word “law”] can’t be a rule or regulation, it
means statute. Am I wrong?” The Government’s attorney
responded: “You’re not wrong your honor. I’ll be as clear
as I can. ‘Specifically prohibited by law’ here means stat-
ute.” Oral Arg. Audio in No. 11–3231, at 22:42–23:03; see
also id., at 29:57–30:03 (“Now, as we’ve been discussing
here, we’re not saying here that [the word “law”] needs to
encompass regulations. We’re saying statute.”). Those
                  Cite as: 574 U. S. ____ (2015)           11

                      Opinion of the Court

concessions reinforce our conclusion that the Govern-
ment’s proposed interpretations are unpersuasive.
  In sum, when Congress used the phrase “specifically
prohibited by law” instead of “specifically prohibited by
law, rule, or regulation,” it meant to exclude rules and
regulations. We therefore hold that the TSA’s regulations
do not qualify as “law” for purposes of Section
2302(b)(8)(A).
                                B
   We next consider whether MacLean’s disclosure regard-
ing the canceled missions was “specifically prohibited” by
49 U. S. C. §114(r)(1) itself. As relevant here, that statute
provides that the TSA “shall prescribe regulations prohib-
iting the disclosure of information obtained or developed
in carrying out security . . . if the Under Secretary decides
that disclosing the information would . . . be detrimental
to the security of transportation.” §114(r)(1)(C).
   This statute does not prohibit anything. On the con-
trary, it authorizes something—it authorizes the Under
Secretary to “prescribe regulations.” Thus, by its terms
Section 114(r)(1) did not prohibit the disclosure at issue
here.
   The Government responds that Section 114(r)(1) did
prohibit MacLean’s disclosure by imposing a “legislative
mandate” on the TSA to promulgate regulations to that
effect. See Brief for Petitioner 28, 33; see also post, at 2–3
(SOTOMAYOR, J., dissenting). But the Government pushes
the statute too far. Section 114(r)(1) says that the TSA
shall prohibit disclosures only “if the Under Secretary
decides that disclosing the information would . . . be det-
rimental to the security of transportation.” §114(r)(1)(C)
(emphasis added). That language affords substantial
discretion to the TSA in deciding whether to prohibit any
particular disclosure.
   The dissent tries to downplay the scope of that discre-
12   DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                     Opinion of the Court

tion, viewing it as the almost ministerial task of “identify-
ing whether a particular piece of information falls within
the scope of Congress’ command.” Post, at 3. But deter-
mining which documents meet the statutory standard of
“detrimental to the security of transportation” requires the
exercise of considerable judgment. For example, the Gov-
ernment says that Section 114(r)(1) requires the Under
Secretary to prohibit disclosures like MacLean’s. The
Government also says, however, that the statute does not
require the Under Secretary to prohibit an employee from
disclosing that “federal air marshals will be absent from
important flights, but declining to specify which flights.”
Reply Brief 23. That fine-grained distinction comes not
from Section 114(r)(1) itself, but from the Under Secre-
tary’s exercise of discretion. It is the TSA’s regulations—
not the statute—that prohibited MacLean’s disclosure.
And as the dissent agrees, a regulation does not count as
“law” under the whistleblower statute. See post, at 1.
   The Government insists, however, that this grant of
discretion does not make Section 114(r)(1) any less of a
prohibition. In support, the Government relies on Admin-
istrator, FAA v. Robertson, 422 U. S. 255 (1975). That
case involved the Freedom of Information Act (FOIA),
which requires federal agencies to disclose information
upon request unless, among other things, the information
is “specifically exempted from disclosure by statute.” 5
U. S. C. §552(b)(3). In Robertson, we held that the Federal
Aviation Act of 1958 was one such statute, because it gave
the Federal Aviation Administration (FAA) “a broad de-
gree of discretion” in deciding whether to disclose or with-
hold information. 422 U. S., at 266.
   The Government tries to analogize that case to this one.
In Robertson, the Government says, the FAA’s discretion
whether to disclose information did not preclude a finding
that the information was “specifically exempted” from
disclosure by statute. So too here, the Government says,
                 Cite as: 574 U. S. ____ (2015)           13

                     Opinion of the Court

the TSA’s discretion whether to prohibit disclosure of
information does not preclude a finding that the infor-
mation is “specifically prohibited” from disclosure by
Section 114(r)(1). See Brief for Petitioner 30.
   This analogy fails. FOIA and Section 2302(b)(8)(A)
differ in an important way: The provision of FOIA at issue
involves information that is “exempted” from disclosure,
while Section 2302(b)(8)(A) involves information that is
“prohibited” from disclosure.
   A statute that exempts information from mandatory
disclosure may nonetheless give the agency discretion to
release that exempt information to the public. In such a
case, the agency’s exercise of discretion has no effect on
whether the information is “exempted from disclosure by
statute”—it remains exempt whatever the agency chooses
to do.
   The situation is different when it comes to a statute
giving an agency discretion to prohibit the disclosure of
information. The information is not prohibited from dis-
closure by statute regardless of what the agency does. It
is the agency’s exercise of discretion that determines
whether there is a prohibition at all. Thus, when Section
114(r)(1) gave the TSA the discretion to prohibit the dis-
closure of information, the statute did not create a prohibi-
tion—it gave the TSA the power to create one. And be-
cause Section 114(r)(1) did not create a prohibition,
MacLean’s disclosure was not “prohibited by law” under
Section 2302(b)(8)(A), but only by a regulation issued in
the TSA’s discretion.
   In any event, Robertson was a case about FOIA, not
Section 2302, and our analysis there depended on two
FOIA-specific factors that are not present here. First, we
examined the legislative history of FOIA and determined
that Congress did not intend that statute to affect laws
like the Federal Aviation Act. 422 U. S., at 263–265. In
particular, we noted that the Civil Aeronautics Board had
14   DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                     Opinion of the Court

expressed its view during congressional hearings that the
Federal Aviation Act qualified as an exempting statute
under FOIA, and that “no question was raised or challenge
made” to the agency’s view. Id., at 264–265. But that
legislative history can have no effect on our analysis of
Section 2302(b)(8)(A).
   Second, we said that the Federal Aviation Act could fail
to qualify as an exempting statute only if we read FOIA
“as repealing by implication all existing statutes which
restrict public access to specific Government records.” Id.,
at 265 (internal quotation marks omitted). Then, relying
on the presumption that “repeals by implication are disfa-
vored,” we rejected that interpretation of FOIA. But the
presumption against implied repeals has no relevance
here. Saying that Section 114(r)(1) is not a prohibition
under the whistleblower statute is not the same as saying
that the whistleblower statute implicitly repealed Section
114(r)(1). On the contrary, Section 114(r)(1) remains in
force by allowing the TSA to deny FOIA requests and
prohibit employee disclosures that do not qualify for whis-
tleblower protection under Section 2302(b)(8)(A).
   Ultimately, FOIA and Section 2302(b)(8)(A) are different
statutes—they have different language, different histories,
and were enacted in different contexts. Our interpretation
of one, therefore, has no impact whatsoever on our inter-
pretation of the other.
                               III
   Finally, the Government warns that providing whistle-
blower protection to individuals like MacLean would
“gravely endanger public safety.” Brief for Petitioner 38.
That protection, the Government argues, would make the
confidentiality of sensitive security information depend on
the idiosyncratic judgment of each of the TSA’s 60,000
employees. Id., at 37. And those employees will “most
likely lack access to all of the information that led the TSA
                 Cite as: 574 U. S. ____ (2015)           15

                     Opinion of the Court

to make particular security decisions.” Id., at 38. Thus,
the Government says, we should conclude that Congress
did not intend for Section 2302(b)(8)(A) to cover disclo-
sures like MacLean’s.
   Those concerns are legitimate. But they are concerns
that must be addressed by Congress or the President,
rather than by this Court. Congress could, for example,
amend Section 114(r)(1) so that the TSA’s prohibitions on
disclosure override the whistleblower protections in Sec-
tion 2302(b)(8)(A)—just as those prohibitions currently
override FOIA. See §114(r)(1) (authorizing the TSA to
prohibit disclosures “[n]otwithstanding section 552 of title
5”); see also 10 U. S. C. §2640(h) (“the Secretary of Defense
may (notwithstanding any other provision of law) withhold
from public disclosure safety-related information that is
provided to the Secretary voluntarily by an air carrier for
the purposes of this section”). Congress could also exempt
the TSA from the requirements of Section 2302(b)(8)(A)
entirely, as Congress has already done for the Federal
Bureau of Investigation, the Central Intelligence Agency,
the Defense Intelligence Agency, the National Geospatial-
Intelligence Agency, the National Security Agency, the
Office of the Director of National Intelligence, and the
National Reconnaissance Office.             See 5 U. S. C.
§2302(a)(2)(C)(ii)(I).
   Likewise, the President could prohibit the disclosure of
sensitive security information by Executive order. Indeed,
the Government suggested at oral argument that the
President could “entirely duplicate” the regulations that
the TSA has issued under Section 114(r)(1). Tr. of Oral
Arg. 16–20. Such an action would undoubtedly create an
exception to the whistleblower protections found in Sec-
tion 2302(b)(8)(A).
   Although Congress and the President each has the
power to address the Government’s concerns, neither has
done so. It is not our role to do so for them.
16   DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                   Opinion of the Court

  The judgment of the United States Court of Appeals for
the Federal Circuit is
                                              Affirmed.
                 Cite as: 574 U. S. ____ (2015)            1

                   SOTOMAYOR, J., dissenting

SUPREME COURT OF THE UNITED STATES
                         _________________

                          No. 13–894
                         _________________


      DEPARTMENT OF HOMELAND SECURITY, 

        PETITIONER v. ROBERT J. MACLEAN 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FEDERAL CIRCUIT

                      [January 21, 2015]


   JUSTICE SOTOMAYOR, with whom JUSTICE KENNEDY
joins, dissenting.
   I agree with much of the Court’s opinion. I have no
qualms with the Court’s conclusion that the phrase “spe-
cifically prohibited by law,” as used in the Whistleblower
Protection Act of 1989 (WPA), 5 U. S. C. §2302(b)(8)(A),
does not encompass disclosures prohibited only by regula-
tion. See ante, at 7. Nor do I see any problem in the
distinction the Court draws between statutes that prohibit
information from being disclosed, the violation of which
may preclude application of the WPA, and statutes that
simply exempt information from otherwise-applicable
disclosure requirements, which do not trigger the WPA’s
“prohibited by law” exception. See ante, at 12–13.
   I part ways with the Court, however, when it concludes
that 49 U. S. C. §114(r)(1) does not itself prohibit the type
of disclosure at issue here—the release of information
regarding the absence of federal air marshals on overnight
flights. Ante, at 11. That statute provides, in relevant
part, that the Transportation Security Administration
(TSA) “shall prescribe regulations prohibiting the disclo-
sure of information obtained or developed in carrying out
security . . . if the Under Secretary decides that disclosing
the information would . . . be detrimental to the security of
transportation.” §114(r)(1) (emphasis added).
2     DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                        SOTOMAYOR, J., dissenting

  The Court reasons, first, that Section 114(r)(1) does not
“prohibit anything,” but instead simply “authorizes” the
TSA to prescribe regulations. Ante, at 11. But this con-
tention overlooks the statute’s use of the word “shall,”
which, as we have observed, “generally means ‘must.’ ”
Gutierrez de Martinez v. Lamagno, 515 U. S. 417, 432, n. 9
(1995); see also, e.g., Federal. Express Corp. v. Holowecki,
552 U. S. 389, 400 (2008) (“Congress’ use of the term ‘shall’
indicates an intent to ‘impose discretionless obligations’ ”)
(some internal quotation marks omitted)); A. Scalia & B.
Garner, Reading Law: The Interpretation of Legal Texts
114 (2012) (“[W]hen the word shall can reasonably read as
mandatory, it ought to be so read”). Section 114(r)(1) does
not merely authorize the TSA to promulgate regulations; it
directs it to do so, and describes what those regulations
must accomplish.
  The Court focuses, second, on the fact that Section
114(r) authorizes the TSA to “ ‘decid[e]’ ” whether the
disclosure of a particular item of information would in fact
be “ ‘detrimental to the security of transportation.’ ” Ante,
at 11–12 (emphasis deleted). I certainly agree that this
language vests some discretion in the agency.1 But the
——————
  1 The Court does not address respondent’s alternative argument,

accepted by the Court of Appeals below, that Section 114(r)(1) describes
the information encompassed in its prohibitory scope with insufficient
particularity to qualify the disclosure here as “specifically prohibited by
law” within the meaning of the WPA. Some of the legislative history of
the WPA linked its specificity requirement to the criteria established in
Exemption 3 of the Freedom of Information Act, 5 U. S. C. §552(b)(3),
and the Court of Appeals applied this standard. See 714 F. 3d 1301,
1309 (CA Fed. 2013); see also S. Rep. No. 95–969, pp. 21–22 (1978).
MacLean has offered no argument that a WPA anti-disclosure statute
must define the relevant category of information with any greater
degree of particularity. Assuming the Exemption 3 standard is appli-
cable, I note that Section 114(r) is at least as “specific” as the statutory
provisions we have previously held to satisfy Exemption 3’s require-
ments. See, e.g., Department of Justice v. Julian, 486 U. S. 1, 9 (1988)
(holding that provisions of Federal Rule of Criminal Procedure
                      Cite as: 574 U. S. ____ (2015)                     3

                       SOTOMAYOR, J., dissenting

agency is required to prevent the disclosure of any infor-
mation it determines is within Congress’ prohibition; its
discretion pertains only to identifying whether a particu-
lar piece of information falls within the scope of Congress’
command. In concluding that such residual agency discre-
tion deprives Section 114(r) of prohibitory effect, the Court
overlooks the degree of agency involvement that is neces-
sary in the administration of many antidisclosure stat-
utes. Congress cannot be expected to identify with partic-
ularity each individual document or datum the release of
which it wants to preclude. Often, it will have to leave to
an agency or other enforcing authority the tasks of defin-
ing—perhaps through regulations—exactly what type of
information falls within the scope of the congressional
prohibition, and of determining whether a particular item
of information fits the bill. The enforcing authority may,
as the Court puts it, sometimes be required to make some
“fine-grained distinction[s]” in fulfilling this charge, ante,
at 12, but that does not change the fact that Congress
itself is the source of the prohibition on disclosure.2
   Indeed, Congress appears to have anticipated the need
for agency involvement in the interpretation and enforce-

——————
32(c)(3)(A) and former 18 U. S. C. §4208(c)(1982 ed.) prohibiting disclo-
sure of portions of presentence reports “relat[ed] to confidential sources,
diagnostic opinions, and other information that may cause harm to the
defendant or to third parties” could justify withholding under Exemp-
tion 3 (emphasis added)).
   2 For the same reasons, the agency’s decision that a disclosure con-

travened a statute may not necessarily be determinative in any given
WPA case: Although an agency may no doubt receive deference in the
interpretation and implementation of a prohibitory statute, ultimately
WPA protection will not apply if the agency improperly concluded that
a given disclosure was prohibited by that statute. Cf. CIA v. Sims, 471
U. S. 159, 168–181 (1985) (according deference to Central Intelligence
Agency’s expertise, but engaging in an extended analysis of whether
the particular information the agency refused to disclose fell within the
scope of the statutory prohibition).
4    DEPARTMENT OF HOMELAND SECURITY v. MACLEAN

                   SOTOMAYOR, J., dissenting

ment of antidisclosure statutes at the time it enacted the
WPA. The Senate Report to the WPA identified only two
statutes the violation of which would preclude whistle-
blower protection, the first being Section 102(d)(3) of the
National Security Act of 1947, 61 Stat. 498, which pro-
vided that “the Director of Central Intelligence shall be re-
sponsible for protecting intelligence sources and methods
from unauthorized disclosure.” See S. Rep. No. 95–969,
pp. 21–22 (1978). This example clearly suggests Congress
contemplated that a statute directing an agency to protect
against disclosures and delegating substantial authority to
the agency should nevertheless be deemed to impose the
relevant prohibition. Section 114(r)(1)’s delegation to the
TSA to “decide” whether the release of particular infor-
mation would be “detrimental to the security of transpor-
tation” likewise simply reflects Congress’ recognition of
the inevitable fact that the agency will be tasked, in the
first instance, with enforcing its statutory mandate.
   In sum, with Section 114(r)(1), Congress has required
agency action that would preclude the release of infor-
mation “detrimental to the security of transportation.” In
so doing, Congress has expressed its clear intent to pro-
hibit such disclosures. I would respect its intent, and hold
that a disclosure contravening that mandate is “prohibited
by law” within the meaning of the WPA.
   Having said all that, I appreciate the narrowness of the
Court’s holding. The Court’s conclusion that Section
114(r) does not itself prohibit any disclosures depends
entirely on the statutory language directing the agency to
“prescribe regulations,” and providing that the agency will
“decid[e]” what information falls within the statue’s pur-
view. See ante, at 11. From all that appears in the major-
ity opinion, then, this case would likely have turned out
differently if Section 114(r) instead provided: “The disclo-
sure of information detrimental to the security of trans-
portation is prohibited, and the TSA shall promulgate
                 Cite as: 574 U. S. ____ (2015)            5

                   SOTOMAYOR, J., dissenting

regulations to that effect,” or “The Under Secretary shall
prescribe regulations prohibiting the disclosure of infor-
mation detrimental to the security of transportation; and
such disclosures are prohibited.” I myself decline to sur-
render so fully to sheer formalism, especially where trans-
portation security is at issue and there is little dispute
that the disclosure of air marshals’ locations is potentially
dangerous and was proscribed by the relevant implement-
ing regulation. In so surrendering, however, the Court
would appear to have enabled future courts and Con-
gresses to avoid easily the consequences of its ruling, and
thus to have limited much of the potential for adverse
practical effects beyond this case. But in the interim, at
least, the Court has left important decisions regarding the
disclosure of critical information completely to the whims
of individual employees.
   I respectfully dissent.
