The State of Michigan has enacted legislation authorizing a system for union representation of local governmental employees. A union and a local government employer are specifically permitted to agree to an "agency shop" arrangement, whereby every employee represented by a union— even though not a union member—must pay to the union, as a condition of employment, a service fee equal in amount to union dues. The issue before us is whether this arrangement violates the constitutional rights of government employees who object to public-sector unions as such or to various union activities financed by the compulsory service fees.