SAN FRANCISCO—Attorneys for medical marijuana advocates on Monday sought a temporary restraining order to put a stop to a federal crackdown on California pot dispensaries, claiming the effort by the state's four U.S. attorneys is unconstitutional.

Plaintiffs asked U.S. District Court Judge Donna Ryu in Oakland to issue an order barring the government from arresting or prosecuting patients, dispensary owners or landlords of properties housing dispensaries.

Pot advocates said dispensaries in the San Francisco Bay area would start closing this weekend if a restraining order was not issued.

The state's four federal prosecutors last month announced a broad effort to close pot clubs, in particular by sending letters to landlords who rent space to pot dispensaries threatening to seize their property under federal drug trafficking laws.

Lawsuits filed starting Friday in all four of California's federal court jurisdictions accuse the Department of Justice of entrapping pot providers by reversing its own policy, among other legal issues.

Plaintiffs' attorneys cited a Santa Cruz County medical marijuana cooperative's agreement with federal prosecutors to dismiss its case against the government because the department issued a memo telling U.S. attorneys to defer to states on medical use of the drug.

The lawsuits claim that by introducing the Justice Department's so-called Medical Marijuana Guidance memo as part of that case, prosecutors were essentially laying out their policy on medical marijuana. "They locked themselves in," said San Francisco attorney Matt Kumin, lead attorney on the suits.

Based on the memo issued in 2009, other medical marijuana providers in the state could reasonably assume they would no longer face federal prosecution, the suits argue.

"The conduct of the government officials and their statement led the nation to believe that the government had changed its policy in 2009, ensuring that those who comply with state medical cannabis laws would not be subject to federal prosecution," according to the suits.

The U.S. Attorney's Office for the Northern District of California had no comment, spokesman Jack Gillund said.

Pot advocates hailed the 2009 memo as the fulfillment of an Obama campaign promise to respect state law on medical marijuana. But after a short honeymoon the federal government has steadily moved toward more restrictive marijuana policies, even as more states began permitting legal use of the drug for medical purposes.

The California lawsuits argue that the federal government is also violating the 14th Amendment of the Constitution requiring equal protection under the law because medical marijuana operations in Colorado are not facing a similar crackdown.

The suits claim patients' rights to make their own health decisions are protected by the 9th Amendment, which retains rights for citizens not explicitly spelled out in the Constitution, and that the so-called Commerce Clause of the Constitution prevented the federal government from getting involved in an issue purely related to the in-state marijuana trade.

National medical marijuana advocacy group Americans for Safe Access filed its own suit last month challenging the federal crackdown. That suit claims that recent raids of licensed dispensaries and letters warning city officials they could be prosecuted for trying to regulate medical marijuana cultivation and sales constitute an illegal power grab under the 10th Amendment. The amendment awards to states legislative authority not explicitly reserved for the federal government.

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