 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued May 6, 2013                     Decided July 26, 2013

                        No. 12-1264

   OWNER-OPERATOR INDEPENDENT DRIVERS ASS’N, INC.,
                    PETITIONER

                             v.

 UNITED STATES DEPARTMENT OF TRANSPORTATION, ET AL.,
                    RESPONDENTS


           On Petition for Review of an Order of
      the Federal Motor Carrier Safety Administration


    Paul D. Cullen, Sr. argued the cause for petitioner. With
him on the briefs were Joyce E. Mayers and Paul D. Cullen,
Jr.

    Dana Kaersvang, Attorney, U.S. Department of Justice,
argued the cause for respondents. With her on the brief were
Stuart F. Delery, Principal Deputy Attorney General, Ronald
C. Machen, Jr., U.S. Attorney, Michael S. Raab and Michael
P. Abate, Attorneys, Paul M. Geier, Assistant General
Counsel for Litigation, Federal Motor Carrier Safety
Administration, and Peter J. Plocki, Deputy Assistant General
Counsel for Litigation.
                             2
     Stephan E. Becker and Daron T. Carreiro were on the
brief for amicus curiae The United Mexican States in support
of respondents.

     Before: GARLAND, Chief Judge, BROWN, Circuit Judge,
and SENTELLE, Senior Circuit Judge.

    Opinion for the court filed by Circuit Judge BROWN.

   Dissenting opinion filed by Senior Circuit Judge
SENTELLE.

     BROWN, Circuit Judge: The Owner-Operator Independent
Drivers Association (OOIDA), a trade association, challenges
the decision of the Federal Motor Carrier Safety
Administration (FMCSA) to exempt commercial vehicle
operators licensed in Canada or Mexico from certain statutory
medical certification requirements applicable to drivers
licensed in the United States. The FMCSA claims that
applying these requirements to these foreign drivers would
violate existing executive agreements between those two
countries and the United States. OOIDA cares naught for
these agreements, instead relying on generally applicable
statutory text. The question we must answer is whether a
facially unambiguous statute of general application is enough
to abrogate an existing international agreement without some
further indication Congress intended such a repudiation. We
conclude it is not.

                              I

    Under federal law, “[n]o individual shall operate a
commercial motor vehicle without a valid commercial
driver’s license.” 49 U.S.C. § 31302. Individual states issue
                                3
these licenses, but the federal government specifies
“minimum uniform standards” via regulations contained in 49
C.F.R. Part 383. Id. § 31308; see Int’l Bhd. of Teamsters v.
Peña, 17 F.3d 1478, 1481 (D.C. Cir. 1994). In addition to
obtaining commercial driver’s licenses, U.S. commercial
vehicle operators must receive medical certification verifying
that their “physical condition . . . is adequate to enable them to
operate the vehicles safely.” 49 U.S.C. § 31136(a)(3). For
American drivers, this prerequisite to operating a commercial
vehicle is separate from the process for obtaining a
commercial driver’s license. See 49 C.F.R. § 391.41.

     To facilitate trade, the United States has entered into
“executive agreements” with Mexico and Canada for
reciprocal licensing of commercial drivers operating across
national borders. Executive agreements are not quite treaties;
while the latter require Senate ratification, the former carry
the force of law as an exercise of the President’s foreign
policy powers. See Am. Ins. Ass’n v. Garamendi, 539 U.S.
396, 414–15 (2003). In the case of Mexico, a memorandum of
understanding (“MOU”) enshrined some basic principles from
which to structure regulation, including joint recognition of
U.S. commercial driver’s licenses and Mexico’s “Licencia
Federal de Conductor,” acknowledgment by the United States
of its need to imitate Mexico’s system “for including driver
medical qualification determinations” within the licensing
process, and an understanding that drivers “shall be subject to
the applicable laws and regulations of the country in which
they operate such motor vehicles.” The United States
concluded a similar agreement with Canada in 1998, with the
Federal Highway Administration (FHWA) affirming that “the
medical provisions of the Canadian National Safety Code for
Motor Carriers . . . are equivalent to the medical fitness
                              4
regulations in     the   [Federal   Motor     Carrier   Safety
Regulations].”

     Unlike the American system, which separates medical
certification from the commercial vehicle licensing process,
Mexico and Canada incorporate physical fitness criteria as
part of their licensing regimes. For this reason, the FHWA
treats commercial licenses from these countries as themselves
proof of medical fitness. See Motor Carrier Safety
Regulations: Technical Amendments, 67 Fed. Reg. 61,818,
61,819 (Oct. 2, 2002); Commercial Driver’s License
Reciprocity with Mexico, 57 Fed. Reg. 31,454, 31,455 (July
16, 1992).

     For some time, medical certificates could be issued by
anyone “licensed, certified, and/or registered, in accordance
with applicable State laws and regulations, to perform
physical examinations,” 49 C.F.R. § 390.5 (2011), so long as
the examiner was familiar with the physical demands placed
on commercial motor vehicle operators and was “proficient in
the use of” the federal protocols necessary to conduct the
examination. Id. § 391.43(c) (2011). That changed in 2005
with enactment of the Safe, Accountable, Flexible, Efficient
Transportation Equity Act: A Legacy for Users (the “Act”),
Pub. L. No. 109-59, 119 Stat. 1144. Specifically, § 4116 of
the Act, which governs the “Medical program,” requires the
Secretary of Transportation to “establish and maintain a
current national registry of medical examiners who are
qualified to perform examinations and issue medical
certificates” necessary for drivers of commercial motor
vehicles. 49 U.S.C. § 31149(d)(1). The Act further directs the
Secretary to require all commercial vehicle operators “to have
a current valid medical certificate,” id. § 31149(c)(1)(B), and
“accept as valid only medical certificates issued by persons on
                               5
the national registry,” id. § 31149(d)(3). Section 4116 makes
no mention of the reciprocal agreements with Canada and
Mexico. See 119 Stat. 1726–28, 49 U.S.C. § 31149.

     Several years later, the FMCSA proposed a new rule to
effectuate the Act’s call for a national registry of medical
examiners and to implement more stringent training and
testing requirements. See National Registry of Certified
Medical Examiners, 73 Fed. Reg. 73,129 (Dec. 1, 2008).
Under the proposed rule, only those medical certificates
issued by examiners listed on the registry would be accepted
as valid with one key exception: Mexican and Canadian
drivers operating in the United States would “continue to be
governed by the provisions of existing reciprocity agreements
with Canada and Mexico, because they are not in conflict with
49 U.S.C. 31136(a)(3) and 31149.” Id. at 73,131 n.3.
Meaning, only drivers domiciled in the United States would
need to obtain medical certificates from examiners on the
national registry. OOIDA objected during the comment
period, arguing the Act permitted of no such “exemption.”
The FMSCA rejected OOIDA’s complaint in its final rule. See
National Registry of Certified Medical Examiners, 77 Fed.
Reg. 24,104, 24,110–11 (Apr. 20, 2012) (“Final Rule”).

     Having filed a petition for review, OOIDA now asks this
Court to set aside that portion of the Final Rule specifying that
the national registry requirements do not apply to the medical
certification of properly licensed Canadian and Mexican
drivers.

                               II

    The Constitution places treaties and federal statutes on
equal legal footing—both are “the supreme Law of the Land.”
                              6
U.S. CONST. art. VI, cl. 2. Courts therefore approach conflicts
between treaties and statutes the way they would a conflict
between two treaties or two statutes: the more recent legal
pronouncement controls. Whitney v. Robertson, 124 U.S. 190,
194 (1888). This is known as the last-in-time rule. Kappus v.
Comm’r of Internal Revenue, 337 F.3d 1053, 1057 (D.C. Cir.
2003). But though the last-in-time rule tells courts how to
resolve clashes between statutes and treaties, courts prefer to
avoid such conflicts altogether. Thus, we presume that newly
enacted statutes do not automatically abrogate existing
treaties. See South Dakota v. Bourland, 508 U.S. 679, 687
(1993). The same principles govern the Executive Branch
agreements with Mexico and Canada, even though they were
not formal treaties ratified by the Senate. See, e.g.,
Weinberger v. Rossi, 456 U.S. 25, 31 (1982).

     In this case, the Act speaks in general yet textually
unambiguous terms. Operators of commercial motor vehicles
must have “a current valid medical certificate,” 49 U.S.C.
§ 31149(c)(1)(B), and only a medical examiner listed on the
“national registry” may issue one, id. § 31149(d). No
exception is made for those drivers living in Canada or
Mexico who operate their vehicles within the United States.
But does such language sufficiently express Congress’s intent
to abrogate the executive agreements with Canada and
Mexico? On this question, the case law is murky. There have
been cases in which ambiguous statutes were interpreted to
preserve preexisting treaties or executive agreements, see,
e.g., Weinberger, 456 U.S. at 28–32, and there have been
cases in which unambiguous statutes expressly overrode
international agreements, see, e.g., Kappus, 337 F.3d at
1057–58. But the parties cite no case of quite this kind: a
textually clear statute with no express reference—or any other
                                7
indication of its intended          application—to    conflicting
international agreements.

     OOIDA and the government conceptualize the
presumption against implicit abrogation of international
agreements in different ways. OOIDA views it as no more
than an interpretive aid akin to the rule of lenity: applicable
only to choose among multiple possible readings of a textually
ambiguous statute. Cf. Skilling v. United States, 130 S. Ct.
2896, 2932 (2010). The government, on the other hand, sees it
as a clear statement rule demanding that a statute expressly
abrogate an international agreement before the last-in-time
rule applies. Cf. Gregory v. Ashcroft, 501 U.S. 452, 461
(1991) (“[T]he requirement of clear statement assures that the
legislature has in fact faced, and intended to bring into issue,
the critical matters involved in the judicial decision.” (internal
quotation marks omitted)). OOIDA’s interpretation, the
government warns, “call[s] into question the United States’
ability to import and export hundreds of billions of dollars of
goods across its borders.” Resp’ts’ Br. 29. Because judicial
pronouncements have vacillated between these two positions,
we sympathize with the parties’ confusion but ultimately
agree with the government: absent some clear and overt
indication from Congress, we will not construe a statute to
abrogate existing international agreements even when the
statute’s text is not itself ambiguous.

                                A

     Both our precedents and the Supreme Court’s routinely
characterize the presumption against implicit abrogation of
international agreements as a clear statement rule. See Trans
World Airlines, Inc. v. Franklin Mint Corp., 466 U.S. 243,
252 (1984) (“Legislative silence is not sufficient to abrogate a
                                  8
treaty.”); Weinberger, 456 U.S. at 32 (“We think that some
affirmative expression of congressional intent to abrogate the
United States’ international obligations is required . . . .”);
Washington v. Wash. State Commercial Passenger Fishing
Vessel Ass’n, 443 U.S. 658, 690 (1979) (“Absent explicit
statutory language, we have been extremely reluctant to find
congressional abrogation of treaty rights.”); Cook v. United
States, 288 U.S. 102, 120 (1933) (“A treaty will not be
deemed to have been abrogated or modified by a later statute
unless such purpose on the part of Congress has been clearly
expressed.”); Roeder v. Islamic Republic of Iran (“Roeder I”),
333 F.3d 228, 238 (D.C. Cir. 2003) (“Executive agreements
are essentially contracts between nations, and . . . are expected
to be honored by the parties. Congress (or the President acting
alone) may abrogate an executive agreement, but legislation
must be clear to ensure that Congress—and the
President—have considered the consequences.”); see also
Roeder v. Islamic Republic of Iran (“Roeder II”), 646 F.3d 56,
61 (D.C. Cir. 2011) (expressly describing the presumption as
a “clear statement requirement”). In one case, the Supreme
Court even held an ambiguous treaty provision survived a
later-enacted statute of general scope. See Menominee Tribe of
Indians v. United States, 391 U.S. 404, 406 n.2, 410–12
(1968). 1 And crucially, the Court never deemed this later


     1
        In Menominee Tribe, the Court also found relevant language
in a related statute enacted by the same legislators that did expressly
preserve existing treaty rights. 391 U.S. at 410–411. Analogously,
we note that § 7105 of the Act expressly subjected Mexican and
Canadian commercial vehicle operators to the same regulatory
requirements drivers based in the United States face—at least with
respect to transporting hazardous material. See 49 U.S.C.
§ 5103a(h). Though not automatically conclusive, this provision
suggests that when Congress wished Mexican and Canadian drivers
                                9
statute ambiguous; much like the Act, it spoke in clear, albeit
general, terms. See id. at 408; cf. Trans World Airlines, 466
U.S. at 252–53 (holding that Congress’s repudiation of the
gold standard, which offered the unit of account for enforcing
a treaty, did not preclude an agency from continuing to adopt
regulations for the treaty’s enforcement).

     That said, there are some choice passages in the case law
bolstering OOIDA’s weaker version of the presumption. See
Whitney, 124 U.S. at 194 (“[C]ourts will always endeavor to
construe” treaties and statutes “so as to give effect to both, if
that can be done without violating the language of
either . . . .”); Fund for Animals, Inc. v. Kempthorne, 472 F.3d
872, 879 (D.C. Cir. 2006) (“Courts apply a statute according
to its terms even if the statute conflicts with a prior treaty (the
last-in-time rule), but where fairly possible, courts tend to
construe an ambiguous statute not to conflict with a prior
treaty (the canon against abrogation).”); see also S. African
Airways v. Dole, 817 F.2d 119, 124–27 (D.C. Cir. 1987).
Taken at their word, these cases suggest that inasmuch as the
Act’s text is clear, the implication for the executive
agreements is not of judicial concern.

    What might account for these disparate signals in the case
law? We think much turns on how courts have used the term
“ambiguous” over the years. Historically, a court might deem
a statute ambiguous even if its text was not. See, e.g.,
Albernaz v. United States, 450 U.S. 333, 343 (1981) (“[W]e
are not confronted with any statutory ambiguity. To the
contrary, we are presented with statutory provisions which are
unambiguous on their face and a legislative history which


to submit to U.S. regulatory requirements, it made that intention
clear.
                                 10
gives us no reason to pause over the manner in which these
provisions should be interpreted.” (emphasis added)). These
days, textual clarity is usually dispositive. Dubbing some
statute “ambiguous” means only that its text “is reasonably
susceptible to more than one meaning.” McCreary v. Offner,
172 F.3d 76, 82 (D.C. Cir. 1999). Problem is, when dealing
with the presumption against implicit abrogation of
international agreements, many of the older cases employed
the more capacious concept. For instance, in Trans World
Airlines, the Supreme Court invoked the presumption against
implicit abrogation of international agreements in the face of
“ambiguous congressional action” despite a textually
straightforward statute. 466 U.S. at 252 (emphasis added). 2
Compare Chew Heong v. United States, 112 U.S. 536, 549
(1884) (“The utmost that could be said, in the case supposed,
would be that there was an apparent conflict between the mere
words of the statute and the treaty.” (emphasis added)), with
id. (“[T]he court ought, if possible, to adopt that construction
which recognize[s] and save[s] rights secured by the treaty.”).
Ironically, the word “ambiguous”—being susceptible to
multiple meanings—has itself proven to be ambiguous.

     If we are to choose among conflicting dicta, we will opt
for those statements endorsed by the Supreme Court, which
better resemble the government’s position. More than just our
interpretation of the case law, however, supports our
conclusion that the presumption against implicit abrogation is
a clear statement rule. Repudiating an executive agreement

    2
       The Court then proceeded to examine the legislative history
for some indication of Congress’s desire to abrogate existing
agreements. In this case, for what it is worth, the Act’s legislative
history makes no mention of the executive agreements with Canada
and Mexico, let alone an intention to abrogate them. See, e.g., S.
REP. NO. 109-120, at 22 (2005).
                              11
raises concerns similar to those that justify other clear
statement rules. We have previously required clear statements,
for example, for “statutes that significantly alter the balance
between Congress and the President.” Armstrong v. Bush, 924
F.2d 282, 289 (D.C. Cir. 1991). OOIDA’s reading of the Act
impinges on the President’s foreign policymaking domain, as
well as the FMCSA’s role in enforcing that prerogative. And,
much like the presumption against extraterritorial effect,
requiring a clear statement rule with respect to implicit
abrogation of international agreements “serves to protect
against unintended clashes between our laws and those of
other nations which could result in international discord.”
Kiobel v. Royal Dutch Petroleum Co., 133 S. Ct. 1659, 1664
(2013) (internal quotation marks omitted); cf. Diggs v. Shultz,
470 F.2d 461, 466 (D.C. Cir. 1972) (refusing to employ the
presumption against implicit abrogation of treaties because
doing so would “raise questions of foreign policy and national
defense as sensitive as those involved in the decision to honor
or abrogate our treaty obligations”). The same wisdom
counsels that we not presume the Act repudiates the executive
agreements with Mexico and Canada sub silentio.

                              B

     OOIDA’s best case is Fund for Animals, which construed
the Migratory Bird Treaty Reform Act (Reform Act) in light
of existing treaties respecting the protection of migratory
birds. See 472 F.3d at 874–77. That statute repudiated an
earlier decision of this Court holding that, pursuant to U.S.
treaty obligations, the Secretary of the Interior could not
exclude the mute swan from protection. See Hill v. Norton,
275 F.3d 98 (D.C. Cir. 2001). Rejecting the complaint that the
new statute should not be understood to violate the
international agreements on migratory birds, Fund for
                               12
Animals asserted that “the canon of construction that
ambiguous statutes should not be construed to abrogate
treaties . . . . applies only to ambiguous statutes (and as we
have just explained, this statute is not ambiguous).” 472 F.3d
at 878. This language appears to erect precisely the threshold
test OOIDA favors: Look to the statutory text. If it is
unambiguous, ignore any international agreements that may
exist; if it is ambiguous, only then interpret the statute as
consistent with these agreements.

     Several considerations dissuade us from elevating this
dictum to a doctrine. First, this weaker version of the
presumption against implicit abrogation conflicts with the
clear statement rule prescribed by Roeder I and II—two cases
that sandwiched Fund for Animals temporally—as well as
past Supreme Court practice. Second, and more importantly,
the statute in Fund for Animals is readily distinguishable. The
Reform Act included a “sense of Congress” provision voicing
disagreement with this Court’s previous interpretation of the
treaty at issue. See id. at 877. Though the provision asserted
that the new statute offered the true interpretation of the treaty
rather than a repudiation of it, it nonetheless showed
Congress’s express desire to abrogate the treaty’s prior
application. And finally, even without the “sense of
Congress” provision, the Reform Act was obviously
remedial—even its title is a dead giveaway. When it comes to
the present case, however, nothing in the Act speaks so
plainly to Congress’s intent to alter the legal landscape.
Though Fund for Animals may have suggested a more
permissive standard, the Reform Act offered precisely the
express indication of congressional intent a clear statement
rule requires.
                               13
     It stands to reason that if Congress or the President
understood the Act to be a repudiation of the federal
government’s obligations to Mexico and Canada, someone
would have said something. But contrary to what the dissent
claims, our decision is directed by a legal presumption, not an
“inquiry into congressional and presidential motives.”
Dissenting Op. 6. We remain, as ever, guided by the text. In
circumstances like this one that demand a clear statement, part
of the textual analysis involves drawing insight from what
Congress chose not to say along with what it did. In reality, it
is not our treatment of the presumption in this case that the
dissent indicts, but all clear statement rules. After all, any
clear statement rule involves an unwillingness to give full
effect to a statute’s unambiguous text. That is how they work.
See Morrison v. Nat’l Austl. Bank Ltd., 130 S. Ct. 2869, 2878
(2010) (“When a statute gives no clear indication of an
extraterritorial application, it has none.”); Plaut v. Spendthrift
Farm, Inc., 514 U.S. 211, 237 (1995) (“[S]tatutes do not
apply retroactively unless Congress expressly states that they
do.”); Atascadero State Hosp. v. Scanlon, 473 U.S. 234, 241
(1985) (holding that a state constitutional provision providing
that “[s]uits may be brought against the State . . . in such
courts as shall be directed by law” was insufficient to
constitute a waiver of Eleventh Amendment immunity
because such a waiver “must specify the State’s intention to
subject itself to suit in federal court”); id. at 242–46 (holding
that remedies under the Rehabilitation Act for violations by
“any recipient of Federal assistance” did not extend to
violations by a State recipient because Congress did not make
“unmistakably clear in the language of the statute” its
intention to abrogate State immunity).

    Our invocation of the presumption against implicit
abrogation of international agreements is born of common
                                 14
sense. Our dissenting colleague laments how much “harder”
today’s opinion makes it for Congress to override existing
agreements. Dissenting Op. 4. But inserting a phrase like
“notwithstanding any existing international agreement” into a
bill does not threaten to exhaust legislative resources. Like all
clear statement rules, the one we acknowledge today injects
clarity into the policymaking process. It permits Congress, the
President, the courts, and the public alike to better
comprehend the actual implications of legislation. We
therefore presume the Act was not intended to abrogate the
executive agreements with Mexico and Canada and hold that
the FMCSA’s implementing rules appropriately understood
the medical certificate requirement to apply only to drivers
based in the United States.

                                 III

     Having dispensed with OOIDA’s main contention, we
turn now to its secondary argument. In a Wittgensteinian
move, OOIDA attempts to dissolve the controversy
altogether—at least with respect to Mexican drivers 3 —by
contending there is no conflict between the MOU and general
application of the Act’s national registry requirement. OOIDA
invokes the interplay of the MOU’s Articles 3 and 4:

        Article 3

    3
       It is not entirely clear from its reply brief whether OOIDA
thinks its argument on this point can be generalized to the executive
agreement with Canada. See Reply Br. 3 & n.1. Whatever OOIDA’s
intentions may be, it makes no difference. OOIDA devoted the
entirety of its discussion to the language of the MOU, and we need
not address conclusory arguments that receive no further
development. Cement Kiln Recycling Coal. v. EPA, 255 F.3d 855,
869 (D.C. Cir. 2001) (per curiam).
                               15


       Medical Qualification
       In recognition of the medical qualification
       program for a Licencia Federal de Conductor,
       the United States of America shall conduct a
       comprehensive study of processes for
       including    driver   medical    qualification
       determinations within its commercial driver’s
       licensing process.

       Article 4

       Application of Law
       U.S. and Mexican drivers of motor
       vehicles . . . shall be subject to the applicable
       laws and regulations of the country in which
       they operate such motor vehicles.

OOIDA draws two inferences from this language: first, the
MOU does not dictate “how either country must deal with
medical qualifications or certification of those qualifications”;
and second, “Article 4 of the MOU specifically provided that
driver qualifications are to be determined by the laws of the
country in which they operate.” Pet’r’s Br. 16. OOIDA thus
concludes that requiring Mexican drivers to obtain medical
certificates from examiners on the national registry is
consistent with the MOU.

     OOIDA’s theory flatly ignores Article 2 of the MOU,
which specifies that each country “shall require drivers,
licensed pursuant to its authority, to . . . meet its established
medical standards.” Article 2 also provides that “all
Commercial Driver’s Licenses and Licencias Federales de
Conductor issued pursuant to” this requirement “shall be
                              16
given complete recognition and validity by Federal and State
authorities in both countries.” Thus, the MOU explicitly
requires (1) that Mexican drivers licensed in Mexico must
meet Mexico’s medical standards, and (2) that the United
States must recognize Mexican licenses, which themselves
certify that their holders have satisfied those medical
standards.

     In response to this fairly conclusive language, OOIDA
advances a tortured distinction between meeting “established
medical standards” and possessing certification of that fact. In
other words, Article 2 may require that Mexican drivers
satisfy Mexican medical standards, but a medical examiner on
the U.S. national registry must separately certify that fact—or
so OOIDA believes. Its reading is implausible. The United
States cannot accord Mexico’s Licencia Federal de Conductor
“complete recognition and validity” if it refuses to
acknowledge the medical fitness certification role the license
plays. And certification is itself a part of satisfying
“established medical standards.”

     Even were the MOU’s text insufficiently clear, we draw
insight from the 1992 FHWA rule, which, in implementing
the MOU, treated the Licencia Federal de Conductor as
certification of medical fitness. See Commercial Driver’s
License Reciprocity with Mexico, 57 Fed. Reg. at 31,455.
OOIDA acknowledges FHWA’s longstanding interpretation
but believes it irrelevant to understanding the terms of the
MOU. Not so. “Although not conclusive, the meaning
attributed to treaty provisions by the Government agencies
charged with their negotiation and enforcement is entitled to
great weight.” Sumitomo Shoji Am., Inc. v. Avagliano, 457
U.S. 176, 184–85 (1982); see Kolovrat v. Oregon, 366 U.S.
187, 194 (1961). Mexico’s government sees things similarly,
                              17
see Br. for Amicus Curiae the United Mexican States 6–7, and
the postratification understandings of signatory nations to a
treaty are an additional interpretive aid, see Medellín, 552
U.S. at 507. These principles of treaty interpretation apply all
the more strongly to executive agreements, where no
potentially competing Senate view must be considered. We
reject OOIDA’s efforts to find consistency between the MOU
and application of the Act to Mexican drivers.

                              IV

    For the foregoing reasons, the petition for review is

                                                       Denied.
    SENTELLE, Senior Circuit Judge, dissenting:              The
majority concedes that the statute at issue is capable of only
one interpretation, yet it reaches a result that it concedes is
inconsistent with that interpretation. Because we lack
authority to rewrite Congress’s statutes, I respectfully dissent.

      The Supremacy Clause of the Constitution provides that
“[t]his Constitution, and the Laws of the United States which
shall be made in Pursuance thereof; and all Treaties made, or
which shall be made, under the Authority of the United States,
shall be the supreme Law of the Land.” U.S. Const. art. VI,
cl. 2. The rule of priority contained in the Supremacy Clause
is straightforward: The Constitution trumps those statutes and
treaties which are inconsistent with it. See, e.g., Marbury v.
Madison, 5 U.S. (1 Cranch) 137, 180 (1803); Reid v. Covert,
354 U.S. 1, 16–17 (1957). If statutes or treaties are
inconsistent with other statutes or treaties, the last-in-time rule
applies, and the most recent statute or treaty controls. See,
e.g., Breard v. Greene, 523 U.S. 371, 376 (1998) (per
curiam); Covert, 354 U.S. at 18; Whitney v. Robertson, 124
U.S. 190, 194 (1888). Where a statute potentially conflicts
with a prior treaty, “an ambiguous statute should be construed
where fairly possible not to abrogate a treaty.” Fund for
Animals, Inc. v. Kempthorne, 472 F.3d 872, 878 (D.C. Cir.
2006) (citing Trans World Airlines, Inc. v. Franklin Mint
Corp., 466 U.S. 243, 252 (1984)).

    With these fundamental precepts in mind, this case ought
to be simple. In the 1990s, the executive branch made
agreements with Mexico and Canada that exempted Mexican
and Canadian commercial drivers from a Department of
Transportation (“DOT”) regulation that all commercial
drivers operating commercial vehicles in the United States
must have a current medical certification. In 2005, Congress
passed and the President signed a law requiring all
                               2
commercial motor vehicle operators in the United States “to
have a current valid medical certificate” “issued by persons
on” a newly-created “national registry of medical examiners.”
49 U.S.C. § 31149(c)(1)(B), (d)(3).

     Under the statute, then, all commercial drivers, including
Mexican and Canadian drivers, need a medical certificate
issued by an examiner on the national registry to operate
commercial motor vehicles in the United States. But the
DOT’s promulgated rule, relying on the prior agreements,
exempts Mexican and Canadian drivers from this statutory
requirement.

     Because the statute is last-in-time and clearly inconsistent
with the earlier international agreements, the statute governs.
The DOT rule at issue here would permit Mexican and
Canadian drivers to operate commercial vehicles in the United
States without following the statutory requirements of
§ 31149. It is therefore our obligation to grant the petition for
review and vacate this unlawful rule.

     The majority concedes that the statute is unambiguously
inconsistent with the prior international agreements. The
majority expresses worry about congressional intent, but
given that Congress has passed statutory text that the majority
concedes is inconsistent with the prior agreements,
Congress’s intent is no great mystery. Its statute contradicts
the prior rule. That should be the end of the matter, for
“courts must presume that a legislature says in a statute what
it means and means in a statute what it says there.” Conn.
Nat’l Bank v. Germain, 503 U.S. 249, 253–54 (1992). But the
majority goes on to justify elevating the prior agreements
above the statutory text by manufacturing a heightened clear
statement requirement not found in the Constitution, the
Supreme Court’s precedents, or this court’s precedents.
                               3
     First, the Constitution: “Distorting statutory language
simply to avoid conflicts with treaties would elevate treaties
above statutes in contravention of the Constitution.” Fund for
Animals, 472 F.3d at 879. Yet the court’s decision today goes
beyond distorting statutory language and abrogates it
altogether. The court concedes that there is no other plausible
interpretation of the statute, but then it goes on to hold that
Congress must use some additional magic words to give the
admittedly clear statute effect.

     It has long been understood that the Supremacy Clause
places treaties and statutes on equal footing, which is why
courts have always evaluated conflicts between treaties and
statutes using the last-in-time rule. The court’s holding today
elevates treaties above statutes by making it more difficult for
Congress to abrogate prior treaties than prior statutes. The
political branches can overrule a prior statute by enacting a
new statute inconsistent with the old one. See, e.g., Nat’l
Ass’n of Home Builders v. Defenders of Wildlife, 551 U.S.
644, 662–63 (2007); Posadas v. Nat’l City Bank, 296 U.S.
497, 503 (1936). Both the Supreme Court and this court have
explained that this rule should apply identically to conflicts
between a statute and a treaty. See Chew Heong v. United
States, 112 U.S. 536, 549–50 (1884); S. African Airways v.
Dole, 817 F.2d 119, 126 (D.C. Cir. 1987). Thus, the Supreme
Court has explained: “The Constitution gives [a treaty] no
superiority over an act of Congress in this respect, which may
be repealed or modified by an act of a later date.” The Head
Money Cases, 112 U.S. 580, 599 (1884). The court today
requires the political branches to do more to overrule prior
treaties and international agreements than they would need to
do to overrule prior statutes. There is no warrant in the
Supremacy Clause for this result.
                               4
     This result is especially troubling because the Supremacy
Clause does not expressly encompass international
agreements of the type at issue here. It is undisputed that the
agreements before us were not entered pursuant to the
Constitution’s Treaty Clause. See U.S. Const. art. II, § 2, cl. 2
(giving the President “Power, by and with the Advice and
Consent of the Senate, to make Treaties, provided two thirds
of the Senators present concur”). Nor are they “Laws of the
United States” enacted through bicameralism and
presentment. See id. art. I, § 7, cl. 2. See generally Bradford
R. Clark, Separation of Powers as a Safeguard of Federalism,
79 Tex. L. Rev. 1321, 1334–36 (2001). The Mexican
agreement was made between the U.S. Secretary of
Transportation and the Mexican Secretary of Communications
and Transportation, while the Canadian “agreement” was
contained in letters exchanged between two transportation
bureaucrats in the United States and Canada. If “[d]istorting
statutory language simply to avoid conflicts with treaties
would elevate treaties above statutes in contravention of the
Constitution,” Fund for Animals, 472 F.3d at 879, distorting
statutory language to avoid conflicts with international
agreements even more obviously contravenes the
Constitution.

     It is now harder for Congress to overrule two letters
exchanged between mid-level administrative functionaries
than it would be for Congress to overrule a statute passed by a
majority of the people’s representatives and signed by the
President. Nothing in the Constitution justifies transferring
the people’s right to govern themselves to Transport Canada’s
Director General of Road Safety and Motor Vehicle
Regulation and an Associate Administrator in the U.S.
Department      of     Transportation’s   Federal     Highway
Administration Office of Motor Carriers.            Ours is a
government of laws, not of bureaucrats.
                               5
     Second, the Supreme Court’s precedents: The majority
does not dispute that no Supreme Court decisions require a
clear statement rule. In all the Supreme Court cases relied
upon by the majority in which the Court found no abrogation,
the Court held that the relevant statutory text was ambiguous.
For instance, in Trans World Airlines, there was no direct
conflict between the treaty and the statute, so the Court
refused to find abrogation given that the statute did not speak
to the question at issue. 466 U.S. at 252. Cook v. United
States emphasized that prior practice under the treaty could
resolve only “doubt as to the construction of the” statute. 288
U.S. 102, 120 (1933) (emphasis added). Weinberger v. Rossi
found no abrogation because the crucial word at issue was
ambiguous. 456 U.S. 25, 29–36 (1982).

     By contrast, the statute in this case is “textually
unambiguous,” as the majority concedes. Maj. Op. at 6. The
Supreme Court has spelled out our role in such circumstances:
“When the words of a statute are unambiguous, . . . th[e] first
canon[, that a legislature says in a statute what it means and
means in a statute what it says there] is also the last: judicial
inquiry is complete.” Germain, 503 U.S. at 253–54 (quoting
Rubin v. United States, 449 U.S. 424, 430 (1981)) (internal
quotation marks omitted). The Supreme Court long ago made
clear that “when a law is clear in its provisions, its validity
cannot be assailed before the courts for want of conformity to
stipulations of a previous treaty not already executed.”
Whitney, 124 U.S. at 195. A treaty “‘made by the United
States with any foreign nation . . . is subject to such acts as
Congress may pass for its enforcement, modification, or
repeal.’” Id. (quoting Head Money Cases, 112 U.S. at 599).
Because we are governed by Supreme Court precedents, and
the text of the statute is clear, I would go no further.
                               6
     Third, this court’s precedents: The court’s new clear
statement rule contradicts our own precedents. Never have
we refused to find abrogation of a prior agreement where a
later statute was clearly inconsistent with the agreement. In
fact, as discussed, we have explicitly held that we do not
“distort the plain meaning of a statute in an attempt to make it
consistent with a prior treaty.” Fund for Animals, 472 F.3d at
879 (emphasis omitted).

     Before today, our circuit’s law was that where we have
an “unambiguous statutory mandate,” the prior international
agreement must give way. Dole, 817 F.2d at 125 n.2; see
Fund for Animals, 472 F.3d at 879. Quoting the Supreme
Court, we have called it “wholly immaterial to inquire”
whether Congress departed from the prior agreement “by
accident or design.” Dole, 817 F.2d at 126 (quoting Whitney,
124 U.S. at 195) (emphasis omitted). Yet the majority uses
the international agreements as the governing rule even while
acknowledging that the later statute is unambiguous simply
because it is unsure whether Congress and the President really
meant to abrogate the agreement. See Maj. Op. at 12. In
doing so, the majority departs from our precedents and
fashions an inquiry into congressional and presidential
motives.

     As we recently recalled, a statutory canon of
interpretation serves merely as “an interpretive aid, not an
invitation to rewrite statutes.” Ass’n of Am. R.Rs. v. Dep’t of
Transp., No. 12-5204, slip op. at 14 n.7 (D.C. Cir. July 2,
2013). Accordingly, we have applied the canon against
abrogation of a prior agreement only where the later statute
was ambiguous in relevant respects, and we have always
emphasized the statute’s ambiguity. See, e.g., Roeder v.
Islamic Republic of Iran, 333 F.3d 228, 238 (D.C. Cir. 2003)
(emphasizing that “the legislation itself is silent” on the
                              7
precise point of conflict between the statute and the prior
agreement); Roeder v. Islamic Republic of Iran, 646 F.3d 56,
61 (D.C. Cir. 2011) (“An ambiguous statute cannot supercede
an international agreement if an alternative reading is fairly
possible.” (emphasis added)). The majority concedes that the
statute here is unambiguous. Therefore, the cases on which it
relies are all distinguishable. “The language of the statute is
entirely clear, and if that is not what Congress meant then
Congress has made a mistake and Congress will have to
correct it.” Conroy v. Aniskoff, 507 U.S. 511, 528 (1993)
(Scalia, J., concurring in the judgment).

     Of course, it appears that nothing in the statute would
prohibit the DOT from adding Mexican or Canadian doctors
to the new national registry. Further, the United States could
choose to enter into new agreements with Mexico or Canada
that would address these issues.

    The court’s opinion today departs from the precedents of
the Supreme Court and this circuit, and is not founded in the
Constitution. I respectfully dissent.
