A petition drive in Kern County, California, seeks to challenge a recent law that would close down medical marijuana clinics in the area.

Laws designed to close down medical marijuana dispensaries in other parts of California are also being challenged, The New York Times reports. In San Jose, medical marijuana advocates filed tens of thousands of signatures last week, in an effort to require a referendum on a new law that would regulate marijuana dispensaries.

The Kern County petitions, with 17,000 signatures, were turned in this September, resulting in a temporary suspension of the law. A referendum on the law could be held as early as next spring, the newspaper reports.

Last month, United States attorneys in California told dozens of marijuana dispensaries they must close or face criminal and civil action. The move is part of a crackdown on California’s medical marijuana industry. The attorneys said they would prosecute landlords who rent space to operators of medical marijuana dispensaries.

California legalized medical marijuana in 1996, the first state to do so. There are now 15 other states with similar laws.

In July, the U.S. Justice Department announced that medical marijuana dispensaries and licensed growers located in states with medical marijuana laws are not immune from prosecution for violation of federal drug and money-laundering laws.

Deputy Attorney General James Cole wrote a policy memo to federal prosecutors that states, “Persons who are in the business of cultivating, selling or distributing marijuana, and those who knowingly facilitate such activities, are in violation of the Controlled Substances Act, regardless of state law.”