CA Civ Code Section 9506

If more than one claimant has given a stop payment notice:

(a)

Any number of claimants may join in the same enforcement action.

(b)

If claimants commence separate actions, the court that first acquires jurisdiction may order the actions consolidated.

(c)

On request of the public entity, the court shall require that all claimants be impleaded in one action and shall adjudicate the rights of all parties in the action.