Colorado Gov. John Hickenlooper is asking Attorney General Eric Holder for a clear-cut explanation on how the Obama administration intends to handle changes made Tuesday when voters chose to legalize marijuana for recreational use.
Nearly 55 percent of Colorado voters approved the state constitutional change by voting on a statewide referendum.
The Democratic governor talked with Holder by phone on Friday.
Hickenlooper spokesman Eric Brown said the governor and Holder "emphasized the need for the federal government to articulate what its position will be."
Brown acknowledged a collective "sense of urgency" about a state law that defies federal law but said no agreement has been reached and both sides will continue to talk.
Amendment 64 allows people 21 and older to possess up to an ounce of marijuana, grow six pot plants and over the longer term allows for stores to sell it to recreational users.
Hickenlooper, who opposed the referendum, said earlier in the week, "it's hard to imagine the chaos that would result if state by state you had one state legalizing and one state not legalizing."
Still, he acknowledged that Colorado voters have clearly stated they want marijuana "to be regulated like alcohol."
Colorado Attorney General John Suthers said he plans to talk soon with federal officials and that Hickenlooper has no choice but to certify the election results.
Suthers also said the only possible plan right now is to establish the regulatory structure dictated by the state law, create an agency to facilitate an activity in violation of federal law, "then wait to see if the federal government decides to do anything about it."
He said one question is: Will people who grow marijuana be criminally prosecuted because those contemplating going into the business "need to know."
Suthers also suggested the federal government would not sue the state, and instead prosecute people.
The Justice Department declined to discuss the issue but released a statement saying the agency's enforcement of the Controlled Substances Act "remains unchanged" and that officials are reviewing the ballot initiatives.
Despite what the federal government might or might not do, it could take until 2014 before people can walk into Colorado retail stores and buy pot for recreational purposes.
Though Amendment 64 has provided the blueprint, the state legislature will have to establish rules and a new system for licensing and revenue collection.
In the near future, however, criminal penalties for possession of small amounts in Colorado will be lifted.
Attorney Brian Vincente, co-director of the 2012 Campaign to Regulate Marijuana Like Alcohol, argued the 55 percent in favor of legalizing the recreational use of marijuana shows widespread support in the state.
"That is more voters than voted for President Obama, by quite a few in Colorado," he said.
He also said supporters are confident the state level change will "percolate up to the federal government" and lead to better national policies in the near future.
University of Denver constitutional law professor Sam Kamin said the vote in Colorado and a similar one Tuesday in Washington "goes beyond what happened in the other marijuana states."
Larger Colorado cities such as Denver already have a medical-marijuana program. But Kamin suggests that system is not setup to handle the expected change.
"To go from an industry that serves at most a 120,000 people to one that serves millions plus tourists, plus people driving across the border, it really is going to be something different," he said.