Alaska has made smoking, growing and owning small amounts of marijuana legal, becoming the third US state to decriminalise the recreational use of the drug.
The Republican-leaning state, which narrowly passed the measure in November, on Tuesday followed similar moves by Colorado and Washington states, reflecting a rapidly shifting legal landscape for the drug. It remains illegal under federal law.
Anyone aged 21 or older can now possess up to an ounce of marijuana in Alaska and can grow up to six marijuana plants, three of which can be flowering.
Smoking in public and buying and selling the drug remains illegal – though private exchanges are allowed if money is not involved.
Barack Obama’s justice department has cautiously allowed the experiments to proceed, saying it would look to prosecute a narrower range of marijuana-related crimes, such as sales to children.
But that could change if a more conservative president is elected in 2016, when Alaska’s first marijuana shops are likely to open.
Supporters of the measure say it reflects a sense of personal freedom that resonates with residents in Alaska, a state with a libertarian streak. They also argue that legal sales will generate income and jobs.
“Alaska now has some of the most sensible marijuana laws in the nation,” said Dr Tim Hinterberger, chair of the Campaign to Regulate Marijuana Like Alcohol in a statement.
Alaskan officials, and the state’s alcohol regulatory board, which is due to meet on Tuesday, still have to fill a number of gaps in the legislation – for example a definition of the public places where people cannot light up.
State regulators are still drafting rules covering the taxation and sale of marijuana, which must be adopted by 24 November. Applications for the first business licences will not be accepted until February 2016.
Police have released regular updates on how they will enforce the law.
“Ultimately the concern of the police department is the safety and health of our public,” Anchorage police spokeswoman Jennifer Castro said.
“We want to make sure that people are not operating their vehicle impaired or under the influence of marijuana.”
In November, voters in Oregon approved a similar measure, though the drug will only become legal in July, and a ballot initiative legalising marijuana possession but not retail sales was overwhelmingly approved in Washington DC.