Every member of the bargaining unit would be required to join the union or to pay representational fees to the union that would be the equivalent of dues, as a condition of employment, if the union negotiates such a provision into the collective bargaining agreement. While this is not legally required and would be part of contract negotiations, most unions—including the UAW—argue forcefully for such a provision, and most collective bargaining agreements have such provisions.
See, for example, this type of language as part of the UAW’s contingent faculty contract with Barnard College:
ARTICLE 2
UNION REPRESENTATION AND DUES DEDUCTION
Section I - As a condition of employment, each Unit Member, as defined in Article I -Recognition, will become a member of the Union or pay an agency fee (a service charge as a contribution toward the cost of administration of this Agreement and representation by the Union) to the Union within the later of thirty-one (31) days of the ratification of this Agreement or thirty-one (31) days of the date the Unit Member first becomes an employee of the College.
See also the UAW’s contract for adjunct faculty at New York University:
ARTICLE III - UNION SECURITY AND CHECKOFF
A. All adjunct or part-time faculty who become employed by the University and covered by this Agreement and who fail voluntarily to acquire and maintain membership in the Union, shall be required as a condition of continued employment to pay to the Union each month, beginning no later than thirty-one (31) days after the date of their employment, or after the ratification of this Agreement, whichever is later, an Agency Fee (a service charge as a contribution toward the cost of administration of this Agreement and the representation of adjunct or part-time faculty). The amount of such Agency Fee shall be the equivalent to the amount uniformly required to be paid as dues and initiation fees by those who choose to become members of the Union.
If such a provision becomes part of the contract, then any faculty member who refuses to join or pay representational fees to the union would be subject to termination.