Berkeley, California (D) enacted a rent control ordinance. The Ordinance places strict rent controls on all real property that 'is being rented or is available for rent for residential use in whole or in part. The Ordinance establishes a base rent ceiling reflecting the rents in effect at the end of May 1980. Ps may raise rents from these levels only pursuant to an annual general adjustment of rent ceilings by a Rent Stabilization Board of appointed commissioners or after P is successful in petitioning the Board for an individual adjustment. Ps may be fined or sued by tenants for violation of the Ordinance. Ps a group of landlords owning rental property in Berkeley, brought suit in state court claiming violations of Due Process and Equal Protection Clauses of the Fourteenth Amendment. The Supreme Court's decision in Community Communications Co. v. Boulder, 455 U.S. 40 (1982), led certain amici to raise the question whether the Ordinance was unconstitutional because pre-empted by the federal antitrust laws. The California Supreme Court reviewed violation §1 of the Sherman Act under the per se rules and the rule of reason. The court concluded that their exclusive focus on competition and concern for the selfish motives of private actors failed to give due deference to a municipality's legitimate interest in promoting public health, safety, and welfare. The California Supreme Court found both standards inappropriate and proceeded to apply a standard of its own devising, based upon this Court's Commerce Clause cases. The Court found no conflict, and the Supreme Court granted certiorari.