includes any person who has fulfilled the requirements for membership in such organization who neither has voluntarily withdrawn from membership nor has been expelled from membership after appropriate proceedings consistent with lawful provisions of the constitution and bylaws of such organization. They have signed a membership card. Their status is in effect until the worker resigns. This status is voluntary. Regardless of the contract language, a worker cannot be forced to become a member. This individual is covered by a collective bargaining agreement and still has elected to join the union.