SALEM, ORE. ? A judge on Friday upheld a gay marriage ban adopted by Oregon voters last year, rejecting claims that the amendment made too many changes at once and interfered with local government.

In his ruling, Marion County Circuit Judge Joseph Guimond backed supporters of the law who said the measure only clarified marriage law in a single, simple sentence.

The Oregon amendment, passed overwhelmingly in November 2004 as Measure 36, reads: “It is the policy of Oregon, and its political subdivisions, that only a marriage between one man and one woman shall be valid or legally recognized as a marriage.”

Seventeen other states have similar constitutional bans.

The Defense of Marriage Coalition, which led the effort to pass a gay marriage ban in Oregon, hailed Friday’s ruling as a victory for voters.

“If this language, as simple as it is, had been struck down by the courts, it would have taken away the people’s rights to amend their constitution at all,” said Tim Nashif, political director for the group.

The gay rights group Basic Rights Oregon said it will appeal.

“We continue to believe that Measure 36 was too radical a change to the equal protection clause of the Oregon Constitution to simply be considered an amendment,” said Roey Thorpe, the group’s executive director.

In their lawsuit, opponents had argued that the measure contained too many changes because it not only amended the state constitution to forbid same-sex marriage, but also interfered with local governments’ home-rule rights by barring them from recognizing gay marriages performed elsewhere.

Under Oregon law, a ballot measure can make only one change to the state constitution.

The challengers also claimed the measure was improperly placed on the ballot because it was a constitutional revision, not just an amendment, that “violates the fundamental principles of liberty and justice” by banning same-sex marriage.

Such a change would require a two-thirds vote of the state House and Senate before it could be submitted to voters, they said. The judge disagreed, saying that no court has conclusively defined the difference between an amendment and a revision.

Friday’s ruling was the latest setback for gay rights backers in Oregon, where more than 3,000 marriage licenses were granted to same-sex couples in Multnomah County in spring 2004, until a judge halted the practice.