CA Civ Proc Code Section 676.9

(a)

With respect to a foreign-money claim, recovery of prejudgment or pre-award interest and the rate of interest to be applied in the action or distribution proceeding, except as provided in subdivision (b), are matters of the substantive law governing the right to recovery under the conflict-of-laws rules of this state.

(b)

The court or arbitrator shall increase or decrease the amount of prejudgment or pre-award interest otherwise payable in a judgment or award in foreign money to the extent required by the law of this state governing a failure to make or accept an offer of settlement or offer of judgment, or conduct by a party or its attorney causing undue delay or expense.

(c)

A judgment or award on a foreign-money claim bears interest at the rate applicable to judgments of this state.