A federal appeals court ruled Tuesday that the Justice Department cannot prosecute medical marijuana businesses if those businesses are in compliance with applicable state laws.

The court had been asked to rule on whether the Justice Department had proper authority to press forward with federal drug charges in 10 cases involving medical marijuana dispensaries and growers in California and Washington state.

In 2014, Congress passed a bipartisan measure, known as the Rohrabacher-Farr amendment, prohibiting the Justice Department from using federal funds to prevent states from "implementing their own State laws that authorize the use, distribution, possession, or cultivation of medical marijuana." The agency interpreted the measure to mean only that it couldn't stop state governments from carrying out their medical marijuana laws — not that it couldn't prosecute cases against individuals or businesses in those states.

The Justice Department's interpretation infuriated the bill's sponsors. Last fall, a federal judge issued a scathing rebuke of the DOJ, saying that its reading of the bill "defies language and logic," "tortures the plain meaning of the statute" and is "at odds with fundamental notions of the rule of law."

Today, a three-judge panel of the U.S. Court of Appeals for the 9th Circuit agreed. The panel concluded that "at a minimum, [Rohrabacher-Farr] prohibits DOJ from spending funds from relevant appropriations acts for the prosecution of individuals who engaged in conduct permitted by the State Medical Marijuana Laws and who fully complied with such laws."

The judges emphasized that their ruling rests primarily on the simple, plain-language meaning of the amendment. The judges quote relevant case law: "It is a 'fundamental canon of statutory construction' that, 'unless otherwise defined, words will be interpreted as taking their ordinary, contemporary, common meaning.' " They then go on to quote numerous passages from Merriam-Webster, the American Heritage Dictionary, and the Oxford English Dictionary to interpret the words of the amendment.

The court sent the 10 cases back to lower courts to determine whether the defendants were in compliance with state medical marijuana laws.

The Justice Department did not immediately respond to a request for comment.

Marijuana advocates cheered the decision.

"This is a major blow against the federal government's continuing war on medical marijuana and the people who rely on it for relief," Tom Angell of the Marijuana Majority said in an email.

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