decertify

transitive verb | \ dē-ˈsər-tə-ˌfī \ | de·cer·ti·fy

1. : to withdraw or revoke the certification of decertified the class action suit; especially : to withdraw the certification of (a labor union) as a collective bargaining agent petitions to decertify the union : to withdraw the certification of (a labor union) as a collective bargaining agent petitions to decertify the union

   Note: The National Labor Relations Board will decertify a union after an election in which the majority of members do not support the union or after participation in an illegal strike.