The shift toward legalization of marijuana has gained a lot of momentum in the past few years. By a recent count, more than twenty states have enacted legislation that permits use of one form or another. Most allow only medical use, but Colorado and Washington also permit recreational consumption. For present purposes, I take no position on the policy merits of this development. I do, however, want to point out that the marijuana debate tends to overlook an important issue—namely, federal tolerance for legalization of the sort that has occurred in Colorado and Washington probably places the United States in material breach of international law.

The argument is pretty straightforward: The 1961 Single Convention on Narcotic Drugs provides that parties “shall take such legislative and administrative measures as may be necessary . . . to limit exclusively to medical and scientific purposes the production, manufacture, export, import, distribution of, trade in, use and possession of” cannabis, among other drugs. Having joined the treaty in 1967, the United States is bound to comply. But for the most part, the Obama Administration has chosen not to enforce federal drug laws against recreational consumption in Colorado and Washington, and state authorities in those jurisdictions obviously do not have state prohibitions to enforce. Thus, the United States no longer takes “administrative measures” that are necessary to limit use to medical and scientific purposes. A comparable analysis applies under the 1971 Convention on Psychotropic Substances and the 1988 Convention Against Traffic in Narcotic Drugs and Psychotropic Substances, both of which contain similar provisions and bind the United States as a party.

This argument is neither new nor creative. The UN agency that oversees the treaties’ implementation—the International Narcotics Control Board—has reached the same conclusion. In a message accompanying the INCB’s annual report for 2013, the agency president stated that the federal response to legalization in Colorado and Washington “contravene[s] the provisions of the drug control conventions, which limit the use of cannabis to medical and scientific use only.”

One commentator has argued that federalism excuses the treaty violations by prohibiting the federal government from compelling states to enforce federal law. This claim appears to rely on the Supreme Court’s anti-commandeering principle, which holds that Congress can’t oblige the fifty states to enact or enforce a federal regulatory program, or conscript state officers to enforce federal law. But I’m not persuaded. First, the Court has never applied the principle as a limitation on the treaty power, and there is no consensus on when or even whether it would be appropriate to do so. Second, even if anti-commandeering generally applies in the treaty context, the principle doesn’t excuse the type of breach that is occurring here—i.e., one that arises from the Administration’s decision not to use federal resources to limit marijuana use within the United States to medical and scientific purposes. That decision has absolutely nothing to do with commandeering.

It’s clear, moreover, that federalism does not generally preclude the Administration from taking the kinds of administrative measures that the treaty demands. As Missouri v. Holland explained long ago, the subject-matter limitations that reside in the various clauses of Article I, Section 8 do not apply to the treaty power, so the provisions in question impose a valid obligation. And even if one disagrees with Holland, the Court’s more recent decision in Gonzales v. Raich established that the Commerce Clause includes the power to prohibit the local cultivation and consumption of marijuana. If it wanted to, the Administration could return the United States to compliance by enforcing existing laws that are valid under this precedent.

What, then, are the consequences of the breach? The Single Convention spells out a series of procedures that the INCB can initiate in response, beginning with consultations and ending with discussion of the matter in the UN General Assembly. Although its relevance is less likely, Article 14(d)(2) adds that the INCB may also “recommend to Parties that they stop the import of drugs, the export of drugs, or both, from or to the country or territory concerned, either for a designated period or until the Board shall be satisfied as to the situation in that country or territory.” The primary consequence, then, appears to be reputational—the United States marks itself as a state that violates international drug laws, with possible adverse effects on the willingness of other states to cooperate with our enforcement efforts in related areas. Regardless of what you think about legalization, this is a problem if you care about the international rule of law and the standing of the United States in the international community.