The US Justice Department has rescinded an Obama administration policy that had eased enforcement of federal marijuana laws in states that legalised the drug, instead giving federal prosecutors wide latitude to pursue criminal charges.
The action by Attorney General Jeff Sessions could have damaging consequences for the burgeoning marijuana industry in the six states including California and Colorado that have legalised the drug for recreational use, plus dozens of others that permit medicinal use.
Justice Department officials declined to say whether they might take legal action against those states, saying further steps were "still under consideration."
Federal law still prohibits marijuana even as some states move to legalise it. White House spokeswoman Sarah Sanders said President Donald Trump's top priority was enforcing federal law "whether it's marijuana or immigration."
The policy change, detailed by Sessions in a one-page memo to federal prosecutors nationwide, came three days after California formally launched the world's largest regulated commercial market for recreational marijuana.
The administration's action drew condemnation from marijuana legalisation advocates and politicians in both parties in states where the drug has been legalised. They said it trampled on the rights of voters in those states and created uncertainty about how strictly federal drugs laws will be enforced.
The move raised questions about how it might impact tax revenues in states that permit some form of legal marijuana use. It also created uncertainty for banks, already fearful about business relationships with the marijuana industry because of concerns they might run afoul of anti-money laundering rules.
There has been a surge in legalisation of marijuana at the state level in recent years. Other states that permit the regulated sale of marijuana for recreational use include Washington, Oregon, Alaska, and Nevada. Massachusetts and Maine are on track to do so this year.
The policy put in place under Democratic former President Barack Obama, outlined by then-Deputy Attorney General James Cole in a series of memos, had discouraged federal prosecutors from pursuing marijuana-related criminal cases in states that had legalised the drug.
Sessions said in a statement that the Obama-era policy "undermines the rule of law" and told federal prosecutors in his memo to "follow the well-established principles that govern all federal prosecutions" in deciding which marijuana-related activities to prosecute.