The California Supreme Court ruled Monday that a sex offender residency restriction enacted by voters in 2006 applies to people who were convicted before the measure passed but paroled afterward.

The panel, in a decision issued in San Francisco, by a 5-2 vote rejected a claim by four anonymous parolees who contended the measure was an illegal and unconstitutional retroactive punishment.

At the same time, the court unanimously left open a broader constitutional challenge to the law, which was enacted as Proposition 83 and is sometimes known as Jessica's Law in memory of a Florida girl who was raped and murdered by a convicted sex offender.

The law bars those who have been released from prison and are required to register as sex offenders from living within 2,000 feet of a school or park used by children.

The four anonymous parolees claimed in a lawsuit filed in 2007 that the requirement blocks off most or all of entire cities, including almost all of San Francisco, as residential areas for them.

The state high court said the parolees could continue their constitutional challenge, but must begin their cases at the trial level in county superior courts, because the facts are different in each of the four cases.

The trial courts will be in San Francisco, Santa Clara and San Diego counties, the three counties into which the four men were paroled.

The four parolees contend the measure violates their state and federal constitutional privacy, travel and due process rights.