union security agreement

Definition from Nolo’s Plain-English Law Dictionary

A contract between an employer and a union requiring workers to make certain payments (called "agency fees") to the union as a condition of getting or keeping a job. Although it is illegal to require an employee to join a union, workers may be required to instead pay agency fees if such an agreement is in place. Union security agreements are prohibited in right to work states.

Definition provided by Nolo’s Plain-English Law Dictionary.