CA Prob Code Section 9604

No personal representative is chargeable upon a special promise to answer in damages for a liability of the decedent or to pay a debt of the decedent out of the personal representative’s own estate unless the agreement for that purpose, or some memorandum or note thereof, is in writing and is signed by one of the following:

(a)

The personal representative.

(b)

Some other person specifically authorized by the personal representative in writing to sign the agreement or the memorandum or note.