Seventeen U.S. states and the District of Columbia recognize marijuana as a medicine. But under the last three presidencies, medical marijuana distributors have learned that state-level protection doesn’t preclude federal crackdowns, which have been upheld by the Supreme Court under the Commerce Clause.

In fact, federal courts generally bar any mention of state legality in marijuana cases, deeming it irrelevant. But thanks to a May decision by a federal judge, that could change.

In November 2011, sheriff’s deputies searched a Spokane, Washington, property based on marijuana odor. The case was turned over to the feds with the alleged growers facing a minimum of five years in prison.

Their attorney argued that the search violated the Fourth Amendment because suspected marijuana cultivation does not constitute probable cause for a warrant in Washington, which lets people grow the plant for medical use, unless there is evidence that the grower is exceeding state limits. U.S. District Judge William Nielsen agreed, writing that “a state crime has not been committed simply by possessing or manufacturing marijuana in Washington.” The Justice Department has appealed the decision. 

Meanwhile, the Truth in Trials Act, introduced by Reps. Barney Frank (D-Mass.) and Ron Paul (R-Texas), would “provide an affirmative defense for the medical use of marijuana in accordance with the laws of the various States.”