A business can be a “closed shop” and require payment of a fee. Though you don’t, technically have to be a member. The fees are not “dues” they’re essentially

A business can be a “closed shop” and require payment of a fee. Though you don’t, technically have to be a member. The fees are not “dues” they’re essentially “agency fees” or “fair share fee” that make up for the benefits you’re getting due to the union. The fees are usually very close to Union dues so most people just join to get all the rights. Exceptions are “Right to Work” states which explicitly outlaw closed shops.