SACRAMENTO (AP) – California’s domestic partner law, which gives registered partners many of the same rights and protections of marriage, does not conflict with a voter-approved initiative that defined marriage as between a man and a woman, a state appeals court held Monday.

The law, which was signed in 2003 by former Gov. Gray Davis and went into effect Jan. 1, represents the nation’s most sweeping recognition of domestic partner rights after Vermont’s recognition of civil unions for same-sex couples. It grants registered couples virtually every spousal right available under state law except the ability to file joint income taxes.

The Campaign for California Families, along with the late Sen. Pete Knight, challenged the law, saying it undermines Proposition 22, the 2000 initiative that defined marriage as between a man and a woman. Knight, a Republican from Lancaster who died after the suit was filed, was the author of the measure, which passed with 61 percent of the vote.

The 3rd District Court of Appeal upheld a trial judge’s earlier determination that “the Legislature’s enactment of the domestic partners act did not constitute an amendment of the defense of marriage initiative” in a 26-page ruling issued Monday.

The three-judge panel held that the plain language of the 14-word initiative showed the measure was “intended only to limit the status of marriage to heterosexual couples and to prevent the recognition in California of homosexual marriages.”

But the initiative didn’t express “an intent to repeal our state’s then-existing domestic partners law” or ban future legislation regarding domestic partners.

Marriage and domestic partnerships are not the same, as illustrated in the different rights accorded and the process of entering or ending those relationships, the court said.

“This confirms the commonsense understanding that people in California have that domestic partnership and marriage are different,” said Jenny Pizer, senior counsel for the Lambda Legal Defense and Education Fund. “It’s also an enormous relief for registered partners.”

Randy Thomasson, executive director of the Campaign for California Families, said the decision would be appealed. In addition, he said opponents to same-sex marriage would move for another initiative that would end domestic partnerships.

“This ruling gives impetus to the push for a constitutional amendment to protect marriage from the clutches of judges and politicians,” Thomasson said.