(Olympia, Wash.) A federal judge on Thursday ordered the state of Washington to keep shielding the identities of people who signed petitions to force a vote on expanded benefits for gay couples.

U.S. District Judge Benjamin Settle in Tacoma granted the preliminary injunction involving petitions for Referendum 71 while a related case moves forward on the constitutionality of the state public records act.

The referendum, sponsored by a group called Protect Marriage Washington, asks voters to approve or reject the “everything but marriage” domestic partnership law that state lawmakers passed earlier this year.

In his ruling, Settle said he was “not persuaded that waiver of one’s fundamental right to anonymous political speech is a prerequisite for participation in Washington’s referendum process.”

Brian Zylstra, spokesman for Secretary of State Sam Reed, said that the judge’s decision “is a step away from open government.”

“When people sign a referendum or initiative petition, they are trying to change state law,” he said. “We believe that changing state law should be open to public view.”

A spokesman for the state attorney general’s office, which is representing Reed in the case, said they are weighing whether to appeal the preliminary injunction.

At a hearing before Settle last week, attorneys for Protect Marriage had argued that referendum signers’ names and addresses should be exempt from the public records disclosure law because release of the information would put them at risk of harassment, amounting to an unconstitutional infringement of free speech rights.

Referendum campaign organizer Larry Stickney said he’s already been subjected to threats and harassment for his involvement in the effort. The campaign also said it has heard from supporters who didn’t want to sign the petition for fear of reprisals.

However, Assistant Attorney General Jim Pharris told the judge that Protect Marriage hasn’t shown significant harm beyond rude comments or phone calls – nothing that would “be appropriate to overturning the state’s strong tradition for open government.”

In his ruling, Settle agreed with the state that there must be measures in place to prevent referendum fraud. But because of the secretary of state’s process of verifying signatures, “at this time the court is not persuaded that full public disclosure of referendum petitions is necessary,” the judge said.

Protect Marriage turned in nearly 138,000 signatures in July, with 121,780 being accepted. That was about 1,200 more than the minimum required to qualify for the ballot.

Two gay rights groups, WhoSigned.Org and KnowThyNeighbor.org, previously said they would post the names online, which sparked the legal action to keep them private.

Protect Marriage was unsuccessful in an effort to keep the names of its political donors secret when the state Public Disclosure Commission ruled last month that donors weren’t exempt from campaign finance laws requiring disclosure.

Protect Marriage Attorney Stephen Pidgeon said he was still deciding whether to appeal that decision. But in the meantime, he said that he is happy that the names of those who signed the referendum petitions will not be released.

“The court has said, and said rightly, that the ability to participate, even anonymously, in the political process is a long and respected right in the United States,” he said.

The legal battle to keep the referendum off the Nov. 3 ballot ended Wednesday when supporters of expanded rights for domestic partners said they wouldn’t appeal a Thurston County Superior Court judge’s refusal to block the vote.

Washington Families Standing Together chairwoman Anne Levinson said the group will now focus on a campaign to ensure the law is retained by voters.

After passage by the Legislature, the law was supposed to take effect July 26, but the referendum campaign put it on hold. Now, it will take effect only if approved by voters.

If the law is rejected at the polls, previously enacted legislation on domestic partnerships would remain in place.

More than 5,900 domestic partnership registrations have been filed in Washington since the first law took effect in July 2007.