California Code, Welfare and Institutions Code - WIC § 21006

(a)(1) A supported decisionmaking agreement is effective until it is terminated in one of the following ways:

(2) Any party may choose to terminate their participation in the agreement at any time by providing written or oral notice of the termination to all parties to the agreement. An adult with a disability may terminate a supported decisionmaking agreement by other conduct intended to communicate termination, including by canceling, defacing, obliterating, burning, tearing, or otherwise destroying the supported decisionmaking agreement or directing another in the presence of the adult with a disability to destroy the supported decisionmaking agreement.