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.