Congress may have tried to stop residents of the nation's capital from being able to light up joints with impunity, but lawmakers retreated last week in another important drug-war front: medical marijuana.

The $1 trillion spending bill that passed last week included a provision that blocks the Justice Department from spending any money to enforce a federal ban on growing or selling marijuana in the 23 states that have moved to legalize it for medical use. It marks a huge shift for Congress, which for years had sided with federal prosecutors in their battle with states over the liberalization of drug laws. "The war on medical marijuana is over," Bill Piper, a lobbyist with the Drug Policy Alliance, declared to the Los Angeles Times.

Another leading advocate of legalization, Allen St. Pierre of NORML, was pleased but not quite so jubilant. After all, under President Obama, the Justice Department in the last five years has sharply curtailed its raids on pot growers and sellers. But directives from Washington, he said, had not stopped overzealous prosecutors and DEA agents in parts of California from targeting the largest marijuana dispensaries. Will they follow Congress but not the president? "They will decide whether this comes to be," St. Pierre said by phone, in reference to the prosecutors and the DEA.