Amendment 64, the marijuana legalization initiative that Colorado voters approved yesterday, must be signed into law within 30 days by Gov. John Hickenlooper, who has indicated he will do so. At that point people 21 or older will no longer be arrested or prosecuted under state law for possessing up to an ounce, growing up to six plants, or transferring up to an ounce "without remuneration" to other people who are at least 21. But implementation of a state-licensed commercial distribution system will take another year or so. The Colorado Department of Revenue, which currently regulates the state's medical marijuana dispensaries, is tasked with writing regulations for pot stores by next July. The new law requires the department to begin processing license applications by October and to start issuing licenses by January 2014. "We say the licenses can be issued as soon as October 2013," says Brian Vicente, co-director of the Yes on 64 campaign. "Given the way government runs, we say they must be issued by January 2014. Our best guess is that it's 2014 when these stores will be opening up."

As with medical marijuana dispensaries, the new stores will be licensed not only by the state but also by local governments, which will have the authority to ban cannabis businesses within their boundaries—by a city council vote at any point or by ballot initiative in even-numbered years. "Probably the only retail marijuana shops will be pre-existing dispensaries that decide to opt in to this new system," Vicente says. "What we've found is that communities across Colorado, the ones that have not banned dispensaries, have strictly regulated these medical marijuana stores….I don't think they're going to expand the zoning. In fact, I think the pre-existing dispensaries stand to benefit from opting in to this system in 2014."

Amendment 64's rules for marijuana stores are considerably less detailed than the ones laid out in Intiative 502, the legalization measure approved by Washington voters yesterday—which, among other things, forbids consumption on the premises. Colorado's law, like Washington's, prohibits "public" consumption. But might the Department of Revenue decide to approve more-discreet versions of Amsterdam's cannabis cafés? "That is a possibility," Vicente says. "We don't think the Department of Revenue initially will head down the road of allowing consumption in private clubs. Really this was drafted to allow retail stores and allow individuals to use marijuana privately in their homes."

Can the federal government try to block implementation of the law? "It is possible the federal government will use their scarce resources to try to overturn the will of Colorado voters and prevent these stores from coming on board," Vicente says. "I think they would argue that federal law in some way trumps state law …that there is a positive conflict there, possibly because the state is issuing licenses to grow and sell a substance that is illegal federally." The question of whether licensing pot sellers creates a direct conflict with federal law came up in the legal wrangling over Arizona Gov. Jan Brewer's resistance to implementing that state's voter-approved medical marijuana law. Notably, the U.S. Justice Department did not endorse this claim, getting involved only to argue (along with the ACLU!) that the controversy was not ripe for adjudication. At least one California appeals court has accepted the idea that licensing pot sellers, rather than simply declining to prosecute them (which states have no obligation to do), crosses a line and violates the Controlled Substances Act. But other state appeals courts disagree, and the issue is before the California Supreme Court.

Vicente says the claim that the Controlled Substances Act bars state licensing of marijuana retailers is "a tenuous and weak argument," noting that "there are 18 states, including Massachusetts now, that have medical marijuana, and many of those states have stores that are state licensed and sell marijuana to sick people. So if there were a strong federal case to be brought, I think it already would have happened….According to the federal Controlled Substances Act, there is no medical marijuana. Marijuana is an illegal substance, period. In reality, it's been sold in a state-sanctioned fashion since 1996, when California passed their law, and the federal government has not acted to wholesale prevent that."

It has, of course, harried medical marijuana providers with raids, prosecutions, forfeiture, threats to landlords and banks, and onerous IRS dictates. Will this pattern of harassment intensify once marijuana is officially and openly sold for recreational use? Or will it simply continue at a similar level, especially if, as Vicente suggests, the number of outlets remains about the same and the operations are no more obtrusive than they are now? "I'm cautiously optimistic it will be the opposite," says Vicente, who hopes "the fact that Colorado and Washington have acted to legalize marijuana will send a message to the federal government that they need to back off entirely and let states engage in the responsible regulation of marijuana."