As we reported earlier today, U.S. Attorney General Eric Holder didn't choose his appearance before the Senate Judiciary Committee to share the Justice Department response to marijuana laws in Colorado that contradict federal policy.

The measures contradict international treaties, too, as a new report from an agency affiliated with the United Nations points out. Read it and get more details about Holder's testimony below.

The agency in question is the International Narcotics Control Board, which on Tuesday released its annual report. The document says Amendment 64, which allows Colorado adults age 21 and over to use and possess small amounts of marijuana, poses a "significant challenge" to existing international drug law.

In the report, the board points to a 1961 treaty that says governments must "take such legislative and administrative measures as may be necessary" to prevent illegal drug trafficking and use.

"The Board notes with serious concern the ongoing move towards the legalization of cannabis for non-medical purposes in some parts of the United States and, in particular, the outcomes of recent ballot initiatives that took place in the states of Colorado and Washington in November 2012," the report warns. "The Board stresses the importance of universal implementation of the international drug control treaties by all States parties and urges the Government of the United States to take necessary measures to ensure full compliance with the international drug control treaties in its entire territories."

This same point was made by eight former heads of the Drug Enforcement Administration, who wrote a letter to ranking Senate Judiciary Committee members Patrick Leahy and Chuck Grassley asking that they put Holder on the spot about the Justice Department's actions -- or, in their view, inactions -- related to pot laws in Colorado and Washington. One of the questions they suggested the senators pose was, "What is being done to honor our international drug control treaty obligations, which require the United States as a nation to enforce the law prohibiting the distribution, sale and cultivation of marijuana?"

Here's an excerpt from the letter:

Keeping marijuana illegal is a treaty obligation under the 1961 International Convention on Narcotic Drugs and supported by the two other Conventions: the 1971 Convention on Psychotropic Drugs and the 1988 Anti-Trafficking Convention. The United States was a prime mover of these multilateral treaties and largely responsible for signature ratification by virtually every other country in the world. The President of the International Narcotics Control Board (INCB) has already protested the initiatives in Colorado and Washington. The treaty conflict has not gone unnoticed by Mexico and other Latin American leaders. Mexico's President, Felipe Calderon, declared that the United States has "no moral authority" to insist that other countries enforce drug laws if two states in our nation legalize marijuana.

Continue for more about today's marijuana developments. At today's judiciary committee hearing, Holder said his office is close to a response to changes in Colorado and Washington marijuana laws, after being pressured by Colorado Attorney General John Suthers last week in Washington D.C.

"We're in the last stages of that review, and we're trying to make a determination as to what the policy ramifications are going to be, what our international obligations are. There are a whole variety of things that go into this determination, but the people of [Colorado] and Washington deserve an answer, and you will have one soon," Holder said to the National Association of Attorneys General last week.

No telling how long that may be, though. Colorado officials, including Governor John Hickenlooper, have been pressuring the government for a response for four months. So far, Holder has kept silent about the measures other than to say that marijuana remains a federally illegal Schedule 1 controlled substance.

One outcome could be that the feds don't challenge the laws and allow for a controlled recreational industry to exist. But it could go the other way, with Holder coming out swinging against Colorado and Washington and suing the states, much like what happened with Arizona's immigration laws.

Here's the INCB 2012 annual report.

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