With half or more Americans now favoring legalizing marijuana, President Obama has one bold option that few experts are talking about: Raising the white flag and ending the federal war on pot.

To be sure, many legal experts believe the US Department of Justice instead is preparing to block new regulatory schemes passed by voters last month in Washington and Colorado that legalize and regulate the selling, possession, and use of marijuana. One option is to invoke Article 6 of the Constitution, which says federal law is "the supreme law of the land."

But despite the constraints of the 1970 Controlled Substances Act in which Congress cemented its stance that marijuana is highly dangerous and has no legitimate medical use, the Obama administration does have legal authority to relabel marijuana as either a less dangerous drug or, as Washington and Colorado have done, classify it alongside alcohol as a legal drug. Such a move could partially or wholly end federal marijuana oversight.

"Maybe this will be the moment when the feds are prepared to revisit marijuana prohibition," says Josh Meisel, co-director of the Humboldt Institute for Interdisciplinary Marijuana Research in California. "At the federal level … I could see a scenario of marijuana regulation" ending.

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At the very least, Washington and Colorado have laid a Gordian knot on the President's desk.

How, exactly, does the US respond, given that a recent Gallup poll finds that 63 percent of Americans want the federal government to leave the two states alone? Moreover, legal experts say, the laws are not at their core contradictory to federal policy.

Both state schemes will continue to regulate marijuana in ways designed to curtail, not promote, its use. In Colorado's case, tax revenues will go to local school districts. In Washington, police will be able to pull over stoners and prosecute them for intoxicated driving if they've had too much to smoke.

The legal issues are complex, and any response by the Obama administration could have broad policy repercussions on everything from enforcement priorities to how it would affect international antidrug treaties.

"Should the Justice Department prevail, it would raise the possibility of striking down the entire initiatives on the theory that voters would not have approved legalizing the drug without tight regulations and licensing similar to controls on hard alcohol," writes the New York Times' Charlie Savage.

So far, the only action the federal government has taken is US Attorney Jenny Durkan's stern warning to Washington residents that "growing, selling, or possessing any amount of marijuana remains illegal under federal law."

The fact that hundreds of Seattle pot smokers blew off that warning and lit up unmolested by law enforcement on Thursday, the day the law took effect, underscored how little actual enforcement power the federal government has, given that most pot busts are handled by local and state police. (Seattle police arrested no one and instead referenced the stoner movie "The Big Lebowski" in a statement that said, "The Dude abides, and says, 'Take it inside.'")

To be sure, there is lots of pressure on Obama from law enforcement officials for the administration to take a stern, contradictory view of what voters in Colorado and Washington have done – suggesting concern from the right that a potential legal tipping point is at hand on federal marijuana policy. Yet the political stakes are huge for Obama, who famously wrote about being a member of a pot-smoking "Choom Gang" while a teenager in Hawaii.

“It’s a sticky wicket for Obama,” Bruce Buchanan, a political science professor at the University of Texas at Austin told the New York Times this week, adding that any aggressive move would be seen as “a slap in the face to his base right after they’ve just handed him a chance to realize his presidential dreams.”

Meanwhile, there is a viable path open for Obama to effectively end federal marijuana prohibition, though it could leave him open for criticism that's been leveled at Obama before by Republicans: that he's end-running Congress. At the same time, about 35 percent of Republicans support legalizing marijuana as a states' rights issue, according to Nov. 6 exit polling.

"In theory, the DEA, in consultation with the secretary of health and human services could move to reschedule marijuana – legally, the administration has that power," says Robert Mikos, a law professor and federalism expert at Vanderbilt University, in Nashville. "That said, making it an unscheduled substance would be a very dramatic change. If that were to happen, it would be politically easier to do in the last days of [Obama's] second term."

Would that mean America would instantly become a giant pot bazaar? Hardly.

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"Ending federal oversight of marijuana would in essence just throw it back to the states, and currently we have 30-some states that criminalize simple possession and a dozen or so that have decriminalized it, and now a couple that have completely legalized it," explains Mr. Mikos. "In that case, marijuana [policy] would just become a matter of state law."

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