A medical marijuana advocacy group has sued the U.S. attorney general and the top federal prosecutor in Northern California, asking a federal court to halt recent raids and threats of prosecution that have significantly stepped up the Obama administration’s assault on the state’s 15-year-old program.

Americans for Safe Access, an advocacy group based in Oakland, filed a lawsuit in U.S. District Court in San Francisco that accuses the Obama administration of violating the Constitution’s 10th Amendment by using coercive tactics to interfere with powers that are delegated to the states.

The four U.S. attorneys in California have dramatically ramped up prosecutions against medical marijuana operations and have advised cities and counties that they cannot adopt regulations that, in effect, authorize the distribution of the federally controlled substance.

“They’re not just enforcing marijuana laws, they are doing something extremely unusual in an effort to quash the medical marijuana programs in the various states,” said Joe Elford, chief counsel for Americans for Safe Access. “They’re not allowed to commandeer the lawmaking functions of the state.”

Tracy Schmaler, spokeswoman for U.S. Atty. Gen. Eric Holder, could not be reached for comment. Jack Gillund, spokesman for Melinda Haag, the U.S. attorney for Northern California, said, “We have no comment.”

The 17-page lawsuit takes aim at resolving one of the most critical legal issues that remains unsettled even though voters approved medical marijuana in a ground-breaking initiative in 1996. Because marijuana remains illegal for all uses under federal law, municipalities and states have struggled with how to regulate it for medical use. The federal prosecutors in California have now insisted that cities and counties cannot do anything that actively allows marijuana use, such as permitting dispensaries. A recent California appellate court ruling reached the same conclusion, but other appellate courts in the state have instead ruled that federal law does not trump state medical marijuana laws.

“The federal government has instituted a policy to dismantle the medical marijuana laws of the state of California and to coerce its municipalities to pass bans on medical marijuana dispensaries,” the lawsuit says. “To this end, the government has pursued an increasingly punitive strategy, which has involved criminal prosecutions of medical marijuana providers with Draconian penalties and letters threatening local officials if they implement state law.”

The lawsuit cites several recent examples of U.S. attorneys telling cities and counties that officials could face federal prosecution. It notes that Chico voted to rescind its recently adopted ordinance after a federal prosecutor met with the city attorney, city manager and police chief. City officials in Eureka received a letter saying that its plan to license large-scale cultivation violates federal law. And a federal prosecutor’s warning to Arcata officials led the city to suspend medical marijuana dispensary permits.

Federal agents this month also raided a collective in Mendocino County that has cooperated with a program to regulate growers, cutting down 99 plants. The lawsuit notes that Mark Perillo Sr., a 48-year-old member of the collective who suffers from chronic pain from a degenerative joint disease, was deprived of his share of the harvest. “He will be impeded from obtaining his medicine because no other delivery service provides medical marijuana at the same low cost,” the suit says.

Elford said that his organization would probably seek a preliminary injunction and expects the issue will eventually reach the state Supreme Court. “I do think this is going to move pretty quickly,” he said.