Cal. Civ. Code § 38-12-509

(1) (a) 
A landlord shall not retaliate against a tenant by engaging in any of the
activities specified in subsection (1)(b) of this section in response to the
tenant:

(I) 
Having made a good faith complaint to the landlord, to a nonprofit organization
or third party, or to a governmental agency alleging a condition described by
section 38-12-505 (1) or any condition that materially interferes with the
life, health, or safety of the tenant;

(II) 
Organizing or becoming a member of a tenants' association or similar
organization; or

(III) 
Exercising or attempting to exercise in good faith any right or remedy afforded
to a tenant pursuant to section 38-12-507.

(b) 
Prohibited retaliation includes:

(I) 
Increasing rent or decreasing services;

(II) 
Terminating or not renewing a rental agreement or contract without written
consent of the tenant;

(III) 
Bringing or threatening to bring an action for possession;

(IV) Taking
action that in any manner intimidates, threatens, discriminates against,
harasses, or retaliates against a tenant; or

(V) 
Charging the tenant or seeking to collect from the tenant any fee, cost, or
penalty.

(1.5) A
tenant may assert that the landlord retaliated against the tenant in violation
of subsection (1) of this section as a defense to a landlord's action for
possession, including a landlord's action for possession based on:

(a) A
monetary or nonmonetary violation of the rental agreement;

(b) A
notice to terminate tenancy or vacate;

(c) An
expiration of the tenant's rental agreement; or

(d) The
nonpayment of rent resulting from a retaliatory rent increase.

(1.7) 
To prove a claim or defense under this section, a tenant does not need to prove
that retaliation was the sole reason a landlord engaged in any of the
activities described in subsection (1)(b) of this section; a tenant need only
demonstrate that the tenant's protected activity under subsection (1)(a) of
this section was a motivating factor that influenced the landlord's decision to
engage in any of the activities described in subsection (1)(b) of this section.

(2) If
a landlord retaliates against a tenant in violation of subsection (1) of this
section, the tenant:

(a) 
Shall recover damages in an amount not more than three months' periodic rent or
three times the tenant's actual damages, whichever is greater, plus reasonable
attorney fees and costs; and

(b) May
terminate the rental agreement.

(3) If
a landlord elects to replace a malfunctioning appliance, but does so with a new
appliance that is not identical to the appliance being replaced, there is a
rebuttable presumption in favor of the landlord that the landlord's selection
of a different appliance was not retaliatory so long as the replacement
appliance provides substantially the same features as the original appliance.

(4) 
(Deleted by amendment, L. 2019.)

(5) 
Nothing in this section precludes a landlord from serving a tenant with a
notice to terminate tenancy or a notice to vacate to the extent allowable under
the law.