SACRAMENTO (AP) – Same-sex marriage opponents filed a proposed amendment to the state constitution that would ban same-sex marriage in the state and strip domestic partners of most spousal benefits.

Randy Thomasson, organizer of a group called VoteYesMarriage.com, said May 19 that the far-reaching measure he hopes to qualify for an upcoming election is designed to prevent judges and lawmakers from eroding laws that limit marriage to one man and one woman.

The move comes as California lawmakers debate a bill to legalize same-sex marriage and follows a March ruling by a trial judge in San Francisco who said state laws prohibiting same-sex couples from marrying are unconstitutional.

“The bad guys here are the judges and the politicians. The people are frustrated,” Thomasson said outside the state Capitol. “The people are ready to protect marriage once and for all.”

The amendment’s sponsors must submit nearly 600,000 signatures from voters to the California Secretary of State to qualify the measure for the June 2006 ballot.

Under the proposed amendment, same-sex couples still would be allowed to register as domestic partners, but most of the privileges and responsibilities the state has provided for such unions would be taken away. State and local governments, for example, would no longer be allowed to provide health coverage for the partners of their gay and lesbian employees.

Gay rights supporters described the measure as among the most extreme attempts nationwide to block the gains same-sex couples have made since Massachusetts legalized same-sex marriage a year ago. If passed, it would make California the 20th state with a constitutional prohibition against same-sex marriage.

“It’s extremely mean-spirited and far-sweeping in its effect,” said Thalia Zepatos of the National Gay and Lesbian Task Force. “It’s absolutely ahead of the pack in its viciousness.”

Massachusetts has allowed same-sex marriage since last May. Vermont has offered civil unions to same-sex couples since 2000; Connecticut will begin offering civil unions in October.

Since Jan. 1, domestic partners in California have had all the rights and responsibilities of marriage conferred by the state except the ability to file joint income taxes.

Thomasson said he would seek as much as $2 million in donations from around the world to fund the signature-gathering campaign.

Lorri Jean, chief executive officer of the Los Angeles Gay and Lesbian Center, said gay rights supporters would be ready to mount a vigorous campaign to defeat the amendment if it qualifies for the ballot.

“I’m still in shock, but I have to say the good news is because they are trying to take away every right we have, rights the vast majority of Californians support, I think this is a battle we can win,” she said.

Thomasson’s group filed the initiative May 19 at the attorney general’s office, which is the first step toward qualifying it for the June 2006 ballot. The attorney general will create a title for the measure and write a 100-word summary. Supporters would then be allowed to circulate signature petitions.

The ballot measure mirrors constitutional amendments rejected by the state Legislature a week prior.

As Thomasson made the announcement, one woman clapped among a small group that gathered. A heckler told him to “Go back to Iowa,” and Thomasson ignored a group of high school students on a visit to the Capitol from Colfax, in the Sierra foothills, who asked why he was opposed to two women marrying.

Because it is so broad, the amendment would face stiff legal hurdles even if voters approve it, according to Jean.

A week prior, a federal judge in Nebraska overturned the same-sex marriage ban adopted in that state in November after ruling that its “broad prescriptions,” which included limiting public employee benefits to married spouses, went “far beyond merely defining marriage as between a man and a woman.”