SAN FRANCISCO — People fighting federal marijuana charges have turned to a recent act of Congress that they say should have stopped the US Department of Justice from prosecuting them because they were doing what their states allowed.

Marijuana is illegal under federal law, and the DOJ disagrees with the defendants’ understanding of the new law.

‘‘It’s been the hardest thing I’ve ever had to deal with in my life when you see the government coming down on you for simply trying to be healthy,’’ said Rolland Gregg. He and his family have fought federal charges, arguing that marijuana plants investigators found on their Washington property were for their medicinal use and complied with state law.

A federal appeals court is expected to issue a ruling soon on the scope of the law that could pave the way to end or overturn at least six federal marijuana criminal prosecutions and convictions .

At issue is a Congressional amendment that said the DOJ could not use funding Congress allocated to it for 2015 and 2016 to prevent states that have legalized medical marijuana from implementing laws that permit its use, distribution, and possession. The Court of Appeals for the Ninth Circuit is expected to clarify the amendment.

Associated Press