Cal. Civ. Proc. Code § 996.120

Upon the hearing of the application, the court shall determine whether injury to the beneficiary would result from substitution or release of the surety. If the court determines that release would not reduce the amount of the bond or the number of sureties below the minimum required by the statute providing for the bond, substitution of a sufficient surety is not necessary and the court shall order the release of the surety. If the court determines that no injury would result from substitution of the surety, the court shall order the substitution of a sufficient surety within such time as appears reasonable.