term:

Decertify

decertify vt

-fied
-fy·ing
: to withdraw or revoke the certification of [decertified the class action suit]
;esp
: to withdraw the certification of (a labor union) as a collective bargaining agent [petitions to 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.
de·cer·ti·fi·ca·tion [dē-sər-tə-fə-kā-shən]
n

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.