Voters in Colorado, Oregon, and Washington will consider fully legalizing marijuana for recreational use when they go to the polls next month.

Passage of the measures would set up a potential showdown between the states and federal authorities who have stepped up their efforts to shut down medical marijuana dispensaries in several states including California.

If approved by voters, the full-legalization initiatives would allow adults over the age of 21 to legally purchase and consume small amounts of the controversial plant, reports the New American .

The initiatives are backed by Law Enforcement Against Prohibition (LEAP) , a group of current and retired officers who support decriminalizing marijuana.

Michele Leonhart, the DEA administrator, told law enforcement leaders at the International Association of Chiefs of Police show that decriminalizing marijuana isn't an effective tool in the drug war. She told them LEAP doesn't reflect the view of most officers.

On Tuesday, a group of California medical marijuana activists will challenge the Justice Department's designation of marijuana as a Schedule I drug that's highly addictive with no accepted medical use.

A three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit agreed to hear a half-hour argument by Americans for Safe Access. The Obama administration's Justice Department will argue there are no studies "demonstrating marijuana's safety and effectiveness as a medicine," reports the Mercury News .