<P> A pre-entry closed shop (or simply closed shop) is a form of union security agreement under which the employer agrees to hire union members only, and employees must remain members of the union at all times in order to remain employed . This is different from a post-entry closed shop (US: union shop), which is an agreement requiring all employees to join the union if they are not already members . In a union shop, the union must accept as a member any person hired by the employer . </P> <P> International Labour Organization covenants do not address the legality of closed shop provisions, leaving the question up to each individual nation . The legal status of closed shop agreements varies widely from country to country, ranging from bans on the agreement, to extensive regulation of the agreement to not mentioning it at all . </P> <P> The Taft--Hartley Act outlawed the closed shop in the United States in 1947 . The union shop was ruled illegal by the Supreme Court . States that have passed right - to - work laws go further by not allowing employers to require employees to pay the agency fee . An employer may not lawfully agree with a union to hire only union members, but it may agree to require employees to join the union or pay the equivalent of union dues to it, within a set period after starting employment . Similarly, while a union could require an employer that had agreed to a closed shop contract prior to 1947 to fire an employee who had been expelled from the union for any reason, it cannot demand that an employer fire an employee under a union shop contract for any reason other than failure to pay those dues that are uniformly required of all employees . </P> <P> The United States Government does not permit the union shop in any federal agency regardless of state law allowing for such . </P>

The federal law which made closed shops and preferential shops illegal was the