A union is free to negotiate a contract that only applies to their own members, they just prefer not to so they can prevent non-members from competing using mor

A union is free to negotiate a contract that only applies to their own members, they just prefer not to so they can prevent non-members from competing using more favorable terms. https://en.wikipedia.org/wiki/Members-only_unionism https://en.wikipedia.org/wiki/Members-only_unionism