Marijuana is now legal for recreational use in two US states and will soon be in two more, in addition to the District of Columbia—but it turns out they are all breaking international law.

That’s according to comments made yesterday by Yury Fedotov, executive director of the United Nations Office of Drugs and Crime (UNODC). “I don’t see how (the new laws) can be compatible with existing conventions,” Fedotov told reporters. He has a point.

The US is not-so-subtly breaking a major UN convention

According to the 1961 single convention on narcotic drugs (pdf), which the US signed, countries are prohibited from creating regulated markets for the cultivation, sale, purchase, distribution and possession of marijuana, says Wells Bennett, a national security law fellow at the Brookings Institute and an expert on marijuana policy.

By allowing for the legal sale of marijuana in some states, the US is explicitly breaking the convention, he said. But given that, the state-by-state approach is probably a good strategy.

“The US is being very politically savvy and hedging its bets because if marijuana policy doesn’t work in those US states that have legalized, the political costs for Washington aren’t that big in the short term,” Bennett tells Quartz. “However, this position becomes more difficult to defend if more states legalize and their regulatory regimes are successful and broadly supported by the public.”

If that happens, Bennett says, the US will be seen by the international community as a violator of the treaty it has fought efforts to reform as it continues to promote its “tough on drugs” stance overseas. The status quo it has protected has allowed criminal empires to flourish around the world, destabilizing governments and creating violence, while a “disproportionate burden is placed on weaker states that are home to narcotics production and trafficking,” writes Virginia Comolli for the Council on Foreign Relations.

It’s even breaking its own laws

Under the Controlled Substances Act, the US Drug Enforcement Administration (DEA) classifies marijuana as a schedule 1 substance, along with heroin, ecstasy and other recreational drugs. This classification means that any US state seeking to regulate and distribute marijuana is technically violating federal law.

States have rebelled. Currently, 23 states and the District of Columbia allow marijuana for medicinal use and, in 2012, Washington state and Colorado became the first two states to legalize marijuana for recreational use.

The US Justice Department did not respond with a lawsuit or other tough enforcement measures. Instead, Deputy Attorney General James M. Cole issued a memo (pdf) to federal prosecutors that made it clear that states would be allowed to move forward with establishing their own marijuana policy.

But the US remains a signatory to the 1961 convention and the federal government’s official position is that marijuana is still a schedule 1 substance and illegal under federal law.

The disconnect is emboldening others

The US government’s contradictory position on marijuana has not gone unnoticed at the UN, as illustrated by Fedotov’s comments. Still, the efforts by US states to legalize marijuana have inspired other nations such as Uruguay and Portugal to follow suit, says Mason Tvert, a spokesman for the Marijuana Policy Project, the largest organization working solely on marijuana policy reform in the United States.

“The United States has largely dictated international drug laws for decades, and now that it’s becoming clear that Americans will no longer stand with these failed drug policies, we see other countries moving ahead as well,” Tvert tells Quartz. “Fedotov’s statements may make it awkward for the federal government, but they won’t stop the momentum toward ending marijuana prohibition.”