California Code, Probate Code - PROB § 144

(a) Except as provided in subdivision (b), subject to Section 142, a waiver is enforceable under this section if the court determines either of the following:

(b) If, after considering all relevant facts and circumstances, the court finds that enforcement of the waiver pursuant to subdivision (a) would be unconscionable under the circumstances existing at the time enforcement is sought, the court may refuse to enforce the waiver, enforce the remainder of the waiver without the unconscionable provisions, or limit the application of the unconscionable provisions to avoid an unconscionable result.

(c) Except as provided in paragraph (2) of subdivision (a), subdivision (b) of Section 721 of the Family Code does not apply if the waiver is enforceable under this section.