A potential increase in federal enforcement of laws prohibiting pot sales and usage could put a crimp in California’s budding cannabis industry. Attorney General Jeff Sessions reversed an Obama-era policy that established a hands-off approach to marijuana enforcement in states where it is legal Thursday, the San Francisco Chronicle reports.

Federal prosecutors will now get to decide how aggressively, if at all, to enforce the federal prohibition of cannabis. Under the previous policy, federal officers were not to interfere with legal marijuana sales.

This decision comes days after California’s legalization of recreational pot went into effect and is expected to create additional confusion on how and in what way the federal law will be enforced. Several pot shops began the year with long lines of new customers and additional marijuana businesses are planning to ramp up production.

California’s legal cannabis industry is expected to be one of the largest markets in the world and to generate $1B in tax revenue annually. Seven other states and Washington, D.C., have legalized recreational marijuana while over two dozen states allow medicinal marijuana.

Sessions has long been expected to increase enforcement, especially since he believes marijuana is comparable to heroin and is to blame for spikes in crime, according to the Chronicle. Proponents for legalization have said legalizing the drug would actually reduce crime as it would eliminate the black market, which is often controlled by criminals.

Officials have yet to determine how this decision will impact the legal industry and if it might lead to additional pot-related prosecutions. A separate congressional amendment blocks federal interference in medical marijuana programs, but officials said they also may look into medical marijuana-related charges.