WASHINGTON - Attorney General Jeff Sessions is going after legalized marijuana. Sessions is rescinding a policy that had let legalized marijuana flourish without federal intervention across the country.

That's according to two people with direct knowledge of the decision. They were not allowed to publicly discuss it before an announcement expected Thursday and spoke on condition of anonymity.

The move will leave it to U.S. attorneys where pot is legal to decide whether to aggressively enforce federal marijuana law. The move likely will add to confusion about whether it's OK to grow, buy or use marijuana in states where it's legal, since long-standing federal law prohibits it.

The decision comes days after California began selling recreational marijuana. Today, 29 states have adopted medical marijuana laws. In 2012, Colorado and Washington became the first states to legalize recreational marijuana, and since then, five more states have passed recreational marijuana laws, including Massachusetts, where retail sales are scheduled to begin in July.

This would be a departure from the Obama administration's policy, which issued guidance in 2013 that it would not interfere in state and local initiatives to legalize marijuana, as long as they didn't interfere with federal law enforcement priorities.

Sessions compares marijuana to heroin and blames it for spikes in violence.

The Associated Press contributed to this report.