A full feature on states' efforts to regulate medical marijuana will be online Wednesday with the rest of Governing's August issue.

This November, a longstanding hypothetical could become a reality: one or more states could legalize marijuana use for adults, possibly setting up a conflict with the federal government about states’ rights and drug prohibition.

Residents in Colorado, Oregon and Washington will vote on ballot initiatives to legalize cannabis for commercial use, and early polling suggests at least two have a reasonable chance of passing. A SurveyUSA poll of 630 registered Washington voters this month found 55 percent supported the initiative, while 32 percent were opposed and 13 percent were unsure. A June poll by Rasmussen of 500 likely Colorado voters found 61 percent approved of that state’s initiative; 27 percent disapproved, and 12 percent said they were undecided. The Oregon initiative earned its required number of signatures on July 13, so no immediate polling was available.

Although the proposals differ in some of their specifics, they would each establish licensing and regulation schemes for legal marijuana production and sales to adults 21 and older. State penalties for possession would be eliminated, and excise taxes (similar to those applied to alcohol and tobacco sales) would be enacted.

Policymakers in Colorado and Washington, which already have medical marijuana policies, tell Governing they are comfortable with the prospect of full legalization. “We want to be the first,” says Washington Rep. Roger Goodman, who supports his state’s initiative. “Current law is running headlong into cultural change.”

“The genie is out of the bottle,” says Colorado Sen. Pat Steadman, who drafted legislation to create the state’s medical marijuana regulatory structure in 2010. His state currently has more than 100,000 medical marijuana patients and nearly 600 licensed dispensaries that distribute to them.

Many advocates point to the success of regulated medical cannabis systems like Colorado’s as evidence that full legalization is feasible. And for the first time last October, a Gallup poll found that 50 percent of Americans support national legalization. “The drug warriors picked the wrong side to fight on,” says Mark Kleiman, a UCLA professor who studies marijuana policy and agrees with ending prohibition. “The change has been at all ages. I won’t be stunned if it’s nationally legalized soon.”

There is, of course, one small problem: marijuana is still a Schedule I narcotic under the federal Controlled Substances Act. It’s in the same category as heroin and LSD, regarded as having no medical value and having a high potential for abuse. Under President Barack Obama, federal enforcement against medical marijuana patients has relaxed to a degree, but the White House has stated in numerous letters to state officials that the administration “remains firmly committed to enforcing the (Controlled Substances Act).”

The Obama administration has also said that, in addition to enforcing current law, it opposes any efforts to legalize. As Obama drug czar Gil Kerlikowske famously said in 2009: “Legalization isn’t in the president’s vocabulary.”

The White House hasn’t issued any guidance on the ballot initiatives in Colorado and Washington specifically. Bills to end federal marijuana prohibition have been introduced in recent years by U.S. Rep. Barney Frank (D-Mass.) and U.S. Rep. Ron Paul (R-Texas), but haven’t gained any momentum within the mainstream.

Some policy analysts believe that a state fully legalizing cannabis, thus removing the auspice of medical use that the Obama administration has tolerated, would force the federal government to reconsider its stance. “I think it’s a natural development,” says Robert Mikos, a law professor at the University of Vanderbilt, who has analyzed marijuana laws. “It would become a test case. Let’s show the world that zero-tolerance is faulty, that marijuana is not destroying lives. That’s less of a leap now.”

Barriers to full legalization do exist: for example, the United States has signed international treaties that require the prohibition of marijuana. But academics like Kleiman and Mikos argue that those obligations could be avoided by simply amending or reframing the treaty’s language. “I think that’s a last-ditch argument. You can always abandon the treaty,” Mikos says. “It’s pretty flimsy.”

As the most powerful country in the world, the United States would also be well-positioned to initiate an international overhaul of drug laws. As Kleiman and three co-authors wrote in a new book, “Marijuana Legalization: What Everyone Needs to Know": “There is a belief that international law will not change until the United States wants it to change.”

When will national leaders embrace such a change? For the moment, most politicians “don’t want to spend the political capital” in publicly supporting marijuana legalization, Mikos says. As indicated by the Gallup poll, public opinion is only now coming around in favor of ending prohibition. “It’s still a big political risk,” Mikos says.

Kleiman opines that a high-profile politician—he gave New York Gov. Andrew Cuomo, who supports marijuana decriminalization, as an example—announcing a pro-legalization stance could lead to a flurry of position shifting.

Advocates hope that state action in Colorado, Oregon or Washington this fall will lead to an evolution in federal policy and public perception. “Politicians have to bend to the will of their constituents,” says Allen St. Pierre, executive director of the National Organization for the Reform of Marijuana Laws (NORML), a leading legalization advocacy group. “Marijuana is going to be legal, even if we have to stumble and bumble to get there.”