With a puff of smoke, pot becomes legal in Washington: How will this work?

Pot smokers lit up at Seattle's Space Needle to mark its legalization in Washington. Possessing marijuana, however, is still a federal crime, and it's not clear yet if, or how, federal laws will be enforced.

The end of marijuana prohibition in one corner of the United States came peacefully early Thursday morning as groups of pot smokers lit up underneath the Space Needle in Seattle and police interfered only to suggest that people "responsibly get baked."

For the first time since US prohibition commissioner Harry Anslinger boosted federal marijuana criminalization in 1937 by describing it as a "drug which [makes] men forget their homes and [turns] them into swine," the purchase and use of designated amounts of marijuana for recreational purposes became legal at 12:01 a.m. Thursday in Washington. The state, however, has yet to introduce the regulatory and taxing authorities that will govern the growing and selling of pot.

"A once-unfathomable notion, the lawful possession and private use of pot, [became] an American reality this week," writes Gene Johnson, at the Huffington Post.

Described by one pot activist as the day when the "iron curtain of prohibition" began to come down, the moment had the spirit of liberation for many Americans. Critics, however, voiced concerns about the impact legalization would have on addiction rates and the  availability of marijuana to young people, while the Obama administration weighed its response.

Colorado voters also agreed to legalize – and tax – marijuana on Nov. 6. That state's law will go into effect on Jan. 6.

The US has spent hundreds of billions of dollars to interdict marijuana shipments since Nixon's War on Drugs began in 1971, and last year incarcerated over 800,000 pot-possessing Americans, three-fourths of them for simple possession.

Yet the gradual cultural acceptance of marijuana – a Quinnipiac Poll released this week showed 51 percent of Americans back legalization – laid the groundwork for the states’ referendums, which in turn were buoyed by an unusual coalition of liberals, libertarians, and states' rights conservatives.

Some improbable celebrities also helped the cause, including PBS travel host Rick Steves, as did several former US attorneys and the CEO of Progressive Insurance, Peter Lewis, who pitched in $2 million to the Washington campaign's war chest. International financier George Soros also supported the campaign through groups like the Drug Policy Alliance in New York.

The law passed by referendum in Washington state allows the sale and use of pot, as well as possession of up to an ounce. It also added new regulations against driving while high, including an intoxication limit that can be measured by police after a traffic stop.

The looming question is how the Obama administration will respond to the laws taking effect. So far, the US Justice Department has remained mum about its plans, although the US Attorney's office in Seattle posted a statement on Thursday saying that its "responsibility to enforce the Controlled Substances Act remains unchanged. Neither states nor the executive branch can nullify a statute passed by Congress."

The federal government is waiting in part for the states to actually come up with their regulatory schemes, which will take some time. But given the wording of both laws, it's going to be difficult for the federal government to block the efforts outright, legal experts say.

"These states have been politically and legally astute by passing laws that are tough for the federal government to block, mainly because they're in effect curbing the marijuana market, not facilitating it, which is perfectly consistent with federal law," says Robert Mikos, a Vanderbilt University law professor who has studied how federalism impacts marijuana policy.

"The states can't block the federal government from rounding up and prosecuting residents who violate the Controlled Substances Act, but it's very unlikely that the federal government could wage any direct war on marijuana in these two states,” he says, “because it doesn't have the resources and [may not] have the political will or stomach" to interfere.

"We're at a crossroads here," adds Josh Meisel, co-director of the Humboldt Institute for Interdisciplinary Marijuana Research, in Arcata, Calif.

On one hand, he says, "I'd be surprised if the federal government were not to crack down on what's happening in Washington and Colorado. But I also think this could turn out to be a very significant turning point" where political opportunity and the mainstreaming of pot could cause the federal government to distance itself from marijuana regulation.

One thing is for sure, given the morning celebration in Washington: the federal government can no longer rely on local and state law enforcement to do its drug interdiction in Washington state.

Instead, the Seattle Police Department referenced the film "The Big Lebowski" – a stoner favorite – as it reminded smokers that public toking is still verboten. "The Dude abides, and says, 'Take it inside,' " the department said in a statement.