SACRAMENTO  (AP) — A federal judge has blocked part of a voter-approved ballot initiative related to human trafficking, until a court hearing can be held later this month.

The decision temporarily halts a provision of Proposition 35 that requires registered sex offenders to give authorities a list of their Internet providers and screen names. The initiative, passed Tuesday with 81 percent support, toughens penalties on those convicted of human trafficking.

The American Civil Liberties Union of Northern California and the Electronic Frontier Foundation sued in U.S. District Court in San Francisco on behalf of sex offenders. They argue the requirement restricts offenders' First Amendment right to free speech and their due process and equal protection rights under the Fourteenth Amendment.

U.S. District Judge Thelton Henderson issued a temporary restraining order until there is a full hearing Nov. 20, saying there are "serious questions" of constitutional rights to be considered.

He noted in the four-page order, issued Wednesday, that the state says it can't enforce the provision until March, so there would be minimal harm in issuing a stay.

The lawsuit was filed on behalf of two anonymous registered sex offenders who otherwise would be required to disclose their Internet providers and screen names.

It does not challenge separate provisions in the measure that will more than double prison sentences for human trafficking and impose life sentences for the sex-trafficking of children.

"We do think we'll prevail in the long run," said ACLU staff attorney Michael Risher. "This law simply sweeps much too broadly, because it includes all 73,000 people who are required to register here in California."

The list includes people who committed misdemeanor indecent exposure years ago or whose crimes never involved the Internet, he said.

A sex offender's rights should be restricted only on an individual basis, Risher said, taking into account the offender's history and likelihood of using the Internet to commit new crimes: "It can't dump them all into a category."

Dan Cohen, spokesman for the Yes on 35, said in a statement that the proponents "are confident the court will follow precedent and uphold the new sex offender registration reporting requirements to protect vulnerable women and children from exploitation." They said such court challenges are common and have regularly been rejected by courts.