Civ. Code, § 1997.040

(a) For the purpose of subdivision (a) of Section 1951.2 (damages on termination for breach), the amount of rental loss that could be or could have been reasonably avoided is computed by taking into account any reasonable use of the leased property. However, if the lease contains a restriction on use that is enforceable under this chapter, the computation shall take into account the restricted use of the property except to the extent the tenant proves that under all the circumstances enforcement of the restriction would be unreasonable. The circumstances include, but are not limited to, those involving both the leased property and any building or complex in which it is located.

(b) The remedy described in Section 1951.4 (continuation of lease after breach and abandonment) is available notwithstanding the presence in the lease of a restriction on use of the leased property. The restriction on use applies under Section 1951.4 if it is enforceable under this chapter except to the extent the tenant proves that under all the circumstances enforcement of the restriction would be unreasonable. The circumstances include, but are not limited to, those involving both the leased property and any building or complex in which it is located.