(CNN) -- A legal haze descends on Washington state pot smokers Thursday, when possession of up to an ounce of marijuana by adults becomes legal, but growing and selling it remains a crime.
Initiative 502, passed last month by Washington voters, legalized recreational marijuana use starting December 6, but it will take a year before there are rules for growing and selling it.
"It begs the question, if they can't buy it through a medical marijuana shop, which only people with a prescription and medical marijuana license can, how do they get it?" Washington State Liquor Control Board spokesman Brian Smith said Wednesday.
Growing and selling marijuana will still be prosecuted as a felony, King County Prosecutor Dan Satterberg told CNN.
"So I'm not sure where you're suppose to get it," Satterberg said. "If you stumble across some on the street or it falls from the sky, then you can have it. Otherwise, you are part of a criminal chain of distribution."
Until the state takes over managing marijuana sales, the black market will thrive as it meets consumer demands, Satterberg said.
Recreational pot smokers in Colorado could gain quicker legal access to marijuana thanks to that state's "sophisticated and pretty elaborate" medical marijuana system already in place, Smith said. Gov. John Hickenlooper has up to a month to sign into law Colorado's pot decriminalization initiative after its passage is certified Thursday.
Trafficking in marijuana is still a federal crime, but the governors of Washington and Colorado have appealed to U.S. Attorney General Eric Holder to clarify how the Justice Department will view recreational pot sales in their states.
"We don't want to go and spend serious resources only to have it stopped by the federal government," Smith said. "It would sure help Washington state if they weighed in and made clear their expectations."
The Justice Department is reviewing the new state laws, the U.S. attorney's office said Wednesday. But it said that the department's responsibility to enforce the Controlled Substances Act has not changed.
"Regardless of any changes in state law, including the change that will go into effect on December 6 in Washington state, growing, selling or possessing any amount of marijuana remains illegal under federal law. Members of the public are also advised to remember that it remains against federal law to bring any amount of marijuana onto federal property, including all federal buildings, national parks and forests, military installations and courthouses."
Twenty Colorado business groups have appealed to Holder to enforce federal pot laws, because of questions about how to deal with workers who are high.
"There is uncertainty about our ability to terminate employees if they come to the job impaired," said Sandra Hagen Solin of the Northern Colorado Legislative Alliance. "There are obligations that we have under the drug-free workplace. There are a lot of questions that have arisen."
Satterberg predicted the Justice Department will intervene with a lawsuit, which could drag on for years. Read more: Is medical marijuana safe for children?
Seattle police offered a guidebook explaining Washington's new law.
People 21 and over can possess up to an ounce of marijuana -- or 16 ounces of solid, marijuana-infused product, like cookies, or 72 ounces of infused liquid, like oil -- for personal use, the guide says,
"Please note that the initiative says it 'is unlawful to open a package containing marijuana... in view of the general public,' so there's that," it adds. "Also, you probably shouldn't bring pot with you to the federal courthouse (or any other federal property)."
"The Seattle Police Department will continue to enforce laws against unlicensed sale or production of marijuana, and regulations against driving under the influence of marijuana, which remains illegal," the book says.
Growing marijuana at home and selling it to friends or family remains against the law, the guide says. But, it adds, "In the future, under state law, you may be able to get a license to grow or sell marijuana."
Smoking pot in public, like having an open beer, "could result in a civil infraction -- like a ticket -- but not arrest," it says.
In fact, Seattle police officers have been advised not to take any enforcement action other than to issue a verbal warning, if the new law is violated.
"You can certainly use marijuana in the privacy of your own home," the guide says. "Additionally, if smoking a cigarette isn't allowed where you are (say, inside an apartment building or flammable chemical factory), smoking marijuana isn't allowed there either."
What if an officer suspects a motorist is under the influence of pot?
"If an officer believes you're driving under the influence of anything, they will conduct a field sobriety test and may consult with a drug recognition expert," it says. "If officers establish probable cause, they will bring you to a precinct and ask your permission to draw your blood for testing. If officers have reason to believe you're under the influence of something, they can get a warrant for a blood draw from a judge. If you're in a serious accident, then a blood draw will be mandatory."
No longer will the smell of marijuana emanating from a vehicle lead to a search unless the officer has "information that you're trafficking, producing or delivering marijuana in violation of state law," it says.
Seattle does not hire police officers who have used marijuana in the previous three years, but the department is consulting its lawyers "to see if and how that standard may be revised."
Pot use and possession by anyone under 21 is still a violation of state law. "It may be referred to prosecutors, just like if you were a minor in possession of alcohol," the police guide says.
The ban by universities and colleges on smoking pot on campus is not expected to change.