Cal. Civ. Code § 260

  * § 260. Recovery of rent for certain non-complying premises
restricted during emergency period. 1. Legislative finding. It is hereby
declared that in cities of this state with a population of over one
million there exists an acute shortage of dwelling accommodations
available to low-income families; that many dwellings formerly occupied
by them have been and are continuing to be vacated and demolished
because of structural inadequacy or danger, obsolescence and
dilapidation, or because owners have refused to comply with the law, or
for other reasons; that the freedom of contract has been impaired in
consequence thereof, and unjust, unreasonable and oppressive increases
in the rents of dwelling accommodations available to such families are
being and will continue to be exacted; that world war II has
necessitated an almost complete paralysis of building construction; that
the extent of construction of decent, safe and sanitary dwellings,
conforming with the minimum standards prescribed by law, has failed to
produce a sufficient number of dwellings for the accommodation of
families unable to pay higher rentals; that there has been a rapid
absorption of rentable vacancies in said dwellings and a sharp increase
in rentals; that such communities are threatened with wholesale
evictions; that an emergency exists by reason of these conditions, which
constitute a menace to the health, safety, morals, welfare and comfort
of the citizens of the state, undermine the standard of living of a
large number thereof, tend to impair and impede the enforcement of
existing statutes, cause overcrowding and congestion, foster crime,
encourage the spread of vice and disease and increase the death rate;
that adequate housing accommodations to relieve the hardships and
suffering resulting therefrom cannot be sufficiently provided, with or
without public assistance, during the period of the emergency as herein
declared; and the necessity for legislative intervention, by the
enactment of the provisions of this section and their application until
July first, nineteen hundred forty-nine, is hereby declared as a matter
of legislative determination, and the provisions of this section shall
remain in force and effect only until such date.
  2. For the period during which any old-law tenement or any converted
dwelling shall fail to comply with the applicable provisions of article
six or seven, as the case may be, no rent therefor or for any part
thereof shall be recovered by the owner, nor shall any action or special
proceeding be maintainable for such rent or to recover possession of
such dwelling or part thereof for non-payment of rent, except rent at
such rate as shall not exceed the lowest rent charged therefor for any
month between September thirtieth, nineteen hundred thirty-seven, and
April first, nineteen hundred forty-three.
  3. In any such action or special proceeding in which there shall be
interposed a defense that the dwelling fails to comply with the
applicable provisions of article six or seven or that the rent demanded
exceeds the lowest rent charged for any month between September
thirtieth, nineteen hundred thirty-seven, and April first, nineteen
hundred forty-three, the burden of proof shall be upon the party seeking
to recover rent or possession.
  4. A certification by the department of the results of a search made
by the department shall be admissable as presumptive evidence of the
existence or non-existence of any violation of article six or seven as
in such certificate specified.
  * NB Expired July 1, 1949