The ruling by the Fourth District Court of Appeal in Santa Ana could affect thousands of parolees, the San Francisco Chronicle said.

Proposition 83, a November 2006 initiative called Jessica's Law by its sponsors, contains the residency restriction imposing "traditional banishment under another name," the court said.

The ruling leaves the law in effect but could limit its application.

State law previously prohibited only convicted child molesters from living within a quarter-mile of a school. Prop. 83 makes most densely populated areas of California off limits to paroled sex criminals.

Proposition 83, approved by 70 percent of the voters, bars all registered sex offenders, with crimes ranging from forcible rape to indecent exposure, from living within 2,000 feet of a school or park where children regularly gather, the Chronicle said.