Aclosed union shopis a workplace in which employers agree to hire and employonly workers who are already members of a union. According toHuman Resource Management, 16th Editionby Gary Dessler, this arrangement gives unions significant control over workforce entry by restricting employment exclusively to union members.
Dessler explains that closed shops were once common but are now illegal in the United States under the Taft- Hartley Act. However, understanding the concept remains important for distinguishing it from other union arrangements, such as union shops and agency shops. In contrast, a union shop allows nonunion employees to be hired but requires them to join the union after a certain period.
Options involving voluntary union membership or nonunion-only policies do not define a closed shop.
Therefore, the defining feature of a closed union shop is that ithires and employs current union members exclusively.
Source:
Gary Dessler,Human Resource Management, 16th Edition, Chapter on Labor Relations and Union Structures