(CNN) A Detroit judge has dropped nearly all the charges against a Michigan doctor accused of performing female genital mutilation on at least nine underage girls, according to court documents.

In a decision filed Tuesday, Judge Bernard Friedman ruled that the federal female genital mutilation law is unconstitutional and that Congress did not have the right to criminalize the practice, and therefore he dismissed six of eight charges in the United States' first federal case involving the procedure.

"Congress overstepped its bounds by legislating to prohibit [female genital mutilation]," Friedman wrote, calling it a "local criminal activity" for the states to regulate, not Congress.

Dr. Jumana Nagarwala is the lead defendant in the case. While the charges of conspiring to commit and committing female genital mutilation, as well as aiding and abetting others in doing so, have been dropped, Nagarwala still faces charges of conspiring to travel with intent to engage in illicit sexual conduct and conspiring to obstruct an official proceeding. She was charged alongside Dr. Fakhruddin Attar, his wife, Farida Attar, and five other residents of Michigan and Minnesota.

Her attorney, Shannon Smith, said she and Nagarwala are thrilled with Friedman's decision.

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