SACRAMENTO, Calif. (AP) — Four Northern California gun stores are challenging a state law barring handgun advertisements on windows or other places where they would be visible to the public.

The stores filed the lawsuit Monday in Sacramento federal court, claiming the 91-year-old law violates their free speech rights. They also argue that the law unfairly singles out handguns because similar ads for rifles are allowed.

The lawsuit was filed after a gun store in Tracy, California was cited in September for displaying a handgun advertisement.

A spokesman for the California Attorney General's office declined comment.