California Code, Commercial Code - COM § 1301

(a) Except as otherwise provided in this section, when a transaction bears a reasonable relation to this state and also to another state or nation, the parties may agree that the law either of this state or of the other state or nation shall govern their rights and duties.

(b) In the absence of an agreement effective under subdivision (a), and except as provided in subdivision (c), this code applies to transactions bearing an appropriate relation to this state.

(c) If one of the following provisions specifies the applicable law, that provision governs and a contrary agreement is effective only to the extent permitted by the law so specified: