California Code, Business and Professions Code - BPC § 5536.4

(a) No person may use an architect's instruments of service, as those professional services are described in paragraph (2) of subdivision (b) of Section 5500.1, without the consent of the architect in a written contract, written agreement, or written license specifically authorizing that use.

(b) An architect shall not unreasonably withhold consent to use their instruments of service from a person for whom the architect provided the services.  An architect may reasonably withhold consent to use the instruments of service for cause, including, but not limited to, lack of full payment for services provided or failure to fulfill the conditions of a written contract.