A California statute prohibited employers from using state funds to promote or oppose unions. The purpose statement specified that the state “should not subsidize efforts to assist, promote, or deter union organizing.” But the statute excepted funds used to provide union access to employer facilities, or to negotiate, enter, or carry out voluntary union-recognition agreements. Several organizations (collectively, Chamber of Commerce) (plaintiff) sued the California Department of Health Services (defendant) to enjoin enforcement. Two labor unions intervened to defend the statute, but the court granted the Chamber of Commerce summary judgment. The Ninth Circuit twice affirmed, then granted rehearing en banc and reversed, reasoning Congress did not intend to preclude states from restricting use of their own funds. The Supreme Court granted review.