DENVER (AP) — A U.N. drug agency says the legalization of marijuana for recreational use in Colorado and Washington violates international drug treaties.

The International Narcotics Control Board urged the Barack Obama administration to challenge the legalization measures. It made its appeal in an annual drug report released Tuesday.

U.S. Attorney General Eric Holder said last week that he was in the last stages of reviewing the state laws. Holder said he was examining policy options and international implications of the issue. Marijuana is illegal under federal law.

The federal government could sue the states over legalization or decide not to mount a court challenge.