in the United States, any state law forbidding various union-security measures, particularly the union shop, under which workers are required to join a union within a specified time after they begin employment. The Taft–Hartley Act of 1947 outlawed not the union shop but the closed shop (which can hire union members only) everywhere in the United States. But section 14(b) of the act did encourage the passage of state right-to-work laws by allowing state laws against union-security measures to supersede the federal law.

The strongest support of right-to-work laws generally has come from small business; the 19 states with right-to-work laws in 1966 were concentrated in the South and West and did not include any major industrial state. Indiana was the only industrial state to pass a right-to-work law, but it repealed it in 1965.

Right-to-work laws have periodically become important political issues; in 1966 the Lyndon B. Johnson administration attempted to eliminate such laws by seeking repeal of section 14(b); the effort was thwarted in the Senate with a filibuster led by Senator Everett Dirksen of Illinois.

Supporters of right-to-work laws maintain that they guarantee a person's right to work without being forced to join a union. In addition, they argue that such laws do not weaken the bargaining power of unions but merely permit a worker to bargain on an individual basis if he so chooses. Opponents contend that the name right-to-work law is misleading because such laws do not guarantee employment to anyone. On the contrary, they maintain that such laws tend to reduce workers' job security by weakening the bargaining power of unions.