A federal judge in Detroit on Tuesday declared unconstitutional a U.S. law banning female genital mutilation, and also dismissed several charges against two doctors and others in the first U.S. criminal case of its kind.

U.S. District Judge Bernard Friedman said Congress lacked authority under the Commerce Clause to adopt the 1996 law, and that the power to outlaw female genital mutilation, or FGM, belonged to individual states.

“As despicable as this practice may be, it is essentially a criminal assault,” Friedman wrote. “FGM is not part of a larger market and it has no demonstrated effect on interstate commerce. The Commerce Clause does not permit Congress to regulate a crime of this nature.”