On Monday afternoon, in a conference room off Colfax Avenue in suburban Denver, two dozen members of a government task force will gather to begin hashing out the details of how to create a market for legal, recreational marijuana in the state. The group includes law enforcement officials, public health experts, marijuana advocates and others who have varying opinions but each share a stake in the outcome.

Looming over their task is the fact that growing, possessing and selling pot remains illegal under federal law. Leaders in Colorado and in Washington — the other state where citizens voted in November to legalize marijuana for people older than 21 — have sought guidance from federal officials, but so far they have been met mostly with silence.

President Obama told ABC News’s Barbara Walters in an interview this week that recreational pot smoking in states that have legalized the drug is not a major concern for his administration.

“We’ve got bigger fish to fry,” Obama said. “It would not make sense for us to see a top priority as going after recreational users in states that have determined that it’s legal.”

Those comments provide a glimpse into the president’s thinking, but they hardly remove the legal uncertainty surrounding the issue. Under Obama, the Drug Enforcement Administration has aggressively gone after medical marijuana dispensaries in California, where they are legal. In September, federal officials raided several Los Angeles shops and sent warnings to many more.

“This is a tough problem, because Congress has not yet changed the law,” Obama told Walters of the legalization in Colorado and Washington. “I head up the executive branch; we’re supposed to be carrying out laws. And so what we’re going to need to have is a conversation about, how do you reconcile a federal law that still says marijuana is a federal offense and state laws that say that it’s legal?”

Attorney General Eric H. Holder Jr. said in a speech Wednesday that he would announce a policy on the new state laws “relatively soon,” and a Justice Department spokeswoman on Friday said the marijuana issue is “under review.”

Despite that lingering ambiguity, state officials in Washington and Colorado are pushing forward with plans to put in place a broad legal marijuana market, saying that they must respect the wishes of voters.

Colorado Gov. John Hickenlooper (D) this week signed a declaration formalizing the marijuana legalization measure, known as Amendment 64, which he had publicly opposed. The same day, he signed an executive order creating a task force to find “practical and pragmatic solutions” for implementing it.

Under Amendment 64, Colorado’s department of revenue must begin accepting applications for marijuana business licenses by next October and must begin issuing new licenses by Jan. 1, 2014, or cede that authority to local governments. In Washington state, the state liquor control board has until next December to put in place the procedures for licensing and regulating the drug.

In both places, scores of questions remain. Among them:

How should states regulate the growth and retail sale of pot on a broad scale? How should quality control be overseen? Will there be restrictions on advertising? How should weed be taxed? Where can it be sold? Where can people smoke it? Can employers still test for drugs? How do officials prevent marijuana sales to minors? How should the state amend its laws regarding possession of marijuana? How do lawmakers define when someone is too high to drive?

“It’s going to be a lot of heavy lifting,” said Denver lawyer Christian Sederberg, one of the legalization campaign’s chief organizers and a member of the governor’s implementation task force.

They won’t be starting from scratch. Medical marijuana has been legal in Colorado since 2010, and the state has established an elaborate “seed-to-sale” regulatory scheme that could serve as a blueprint for broader legalization.

“It was really designed to be a model for doing this going forward, and we have a lot we can learn from that,” said Sam Kamin, a University of Denver law professor and another member of the governor’s Amendment 64 task force. “We should use that as a good starting point.”

Denver already has more medical marijuana retailers than Starbucks stores, and about 100,000 residents possess the medical cards necessary to buy pot. That customer base is set to grow exponentially — more than 3 million Colorado residents are older than 21, not to mention potential visitors from other states — and regulating on such a large scale presents new challenges.

“You’re talking about manpower, oversight, quality control. It’s going to be difficult when dealing with a huge number of consumers,” Kamin said. “There are a lot of hard questions we’re going to have to figure out.”

State Sen. Cheri Jahn, a Democrat appointed to the governor’s task force, said many of those questions should have been considered before Amendment 64 ended up on the ballot.

“We should have had hearings on this. We should have had people at the table — medical people, proponents,” said Jahn, who opposed the constitutional amendment. “Whether it’s good or bad is not the issue now; it’s how it gets implemented with good policy. . . . I want it to be very clear so that there’s not 1,000 cases going to court. There has to be real clarity.”

That clarity is unlikely to come, at least entirely, until federal officials specify what tack the government plans to take.

“The biggest question is what the federal government is going to do next. Everything sort of depends on that,” Kamin said. “That will really influence what we are able to do.”

Until more clarity comes, Hickenlooper has said Colorado will press forward. Sederberg, the Amendment 64 proponent, said he is confident that the state can design a safe, efficient system that proves legal marijuana has a legitimate place in American society.

“We’re developing a new industry here, but you can learn from other industries,” he said. “We can regulate anything in this country. If we can regulate pharmaceuticals, if we can regulate alcohol and tobacco, we can certainly do it with this product.”

Rachel Weiner, Philip Rucker and Sari Horwitz contributed to this report.