In a novel decision that could pave the way for other lawsuits, a judge on Tuesday ruled that Harvey Weinstein can be sued for violating a federal sex-trafficking statute by a young actress who claims he coerced her to engage in sex acts with him in exchange for a false promise of a movie role.

The judge said the inducement to have sex with the Hollywood producer could fall under the sex-trafficking law, which makes it a crime to entice and force a person to commit a “commercial sex act” in return for something of value.

Kadian Noble, a British actress, accused Mr. Weinstein in a November lawsuit of sexually assaulting her after he lured her to his hotel room in Cannes, France, in 2014. Mr. Weinstein had promised the actress that they would review her movie reel, but he molested her and forced her to watch him masturbate in the bathroom, she said. Her lawyers argued the incident was legally the same as forced prostitution.

Mr. Weinstein’s lawyers sought to have the suit thrown out. They argued that because nothing of value changed hands, the incident did not fit the definition of sex trafficking. They also contended the suit “would unfairly expand the federal sex trafficking statute to all sexual activity occurring between adults in which one party holds a superior position of power and influence.”