U.S. District Judge Vaughn R. Walker on Thursday kept same-sex marriages on hold in California for at least another week, but suggested that top state officials’ support for gay marriage ultimately may doom any effort to revive Proposition 8.

Walker’s comments were the first public airing of a possibility that has been increasingly under discussion by legal experts — that the fight over the constitutionality of Proposition 8 might not be decided by the U.S. Supreme Court, as many have expected. Instead the case could be brought to an end by the strict legal rules about who is allowed to pursue a dispute in federal court.

Walker’s remarks came in a ruling that would allow same-sex marriages to resume in the state after Aug. 18 unless an appeals court puts them on hold longer.

Last week, Walker declared Proposition 8’s ban on same-sex marriages unconstitutional, saying it violated the gay men and lesbians’ right to equal protection and due process.

The defendants in that case were Gov. Arnold Schwarzenegger and Atty. Gen. Jerry Brown, but they declined to defend the law. As the losing parties, they have authority to appeal Walker’s ruling. But both Brown and Schwarzenegger hailed Walker’s decision and said they would not appeal.

“The governor supports the judge’s ruling,” spokesman Aaron McLear said Thursday.

A private group that opposes same-sex marriage, ProtectMarriage.com, defended Proposition 8 during the trial Walker held earlier this year. The group wants to appeal but may lack legal standing to do so.

To have standing in federal court, a party must show that it has suffered an actual injury, and Walker said no evidence suggests that the campaign would meet that test.

Several outside legal experts have voiced a similar opinion in recent days.

“Proponents may have little choice but to attempt to convince either the governor or the attorney general to file an appeal to ensure jurisdiction,” Walker wrote.

The first test of the standing issue could come as the groups supporting Proposition 8 go the 9th U.S. Circuit Court of Appeals seeking to keep Walker’s ruling on hold — something they vowed to do quickly.

If higher courts agree with Walker on the lack of standing, they would make no decision on the merits of the issue.

The case might still wend through courts on procedural issues for a considerable time, but Walker’s ruling allowing gay marriage would stand as the law in California. It would not have the nationwide impact of a ruling by the U.S. Supreme Court.

Even backers of Proposition 8 concede that the standing issue could doom the effort to reverse Walker’s ruling.

Asked if the Proposition 8 proponents feared they would be denied the right to appeal, Robert H. Tyler, founder and general counsel of Advocates for Faith and Freedom, said: “Everyone prepares for the worst.”

Sponsors of Proposition 8 realized that standing was a “strategic issue, and like any lawsuit, it is rare to find a case where there are not a few bumps along the way,” he added.

UC Berkeley law professor Joan Hollinger said the standing dispute leaves opponents of same-sex marriage in a “really tough spot.” She said the decision last week by Schwarzenegger and Brown not to challenge Walker’s order put the question of standing on “the front burner.”

“This has suddenly come to center stage,” she said.

Chapman University law professor John Eastman, who has been critical of Walker, said ProtectMarriage.com and its allies could try to prove standing by pointing to the fact that the California Supreme Court had given it authority to defend Proposition 8 in state court.

But UC Irvine Law School Dean Erwin Chemerinsky said the effort may be difficult. “Their injury is ideological, and there is a century of precedent that ideological injury is not enough for standing. I think this lets the 9th Circuit and the Supreme Court follow well-established law and avoid the hard constitutional ruling.”

Ironically, the rules on standing have been toughened considerably over the last generation by conservative judges as a way to limit the types of cases that can be brought in federal court.

Backers of Proposition 8 had tried to avoid the standing problem earlier by supporting an effort by Imperial County to intervene in the case. As an issuer of marriage licenses, the county might have a better argument for standing than the measure’s sponsors, some analysts said.

Walker refused to permit the county to intervene, and so far it is not part of the case.

Meanwhile, Walker’s decision to extend the hold on same-sex marriage until at least next week disappointed dozens of gay and lesbian couples who lined up early Thursday throughout the state to marry.

Amanda Pentecost, 25, who waited in West Hollywood to marry Dana Millhollin, 24, said the postponement made her uneasy.

“We have to wait six more days,” Pentecost lamented. “That window can close again for years.”

maura.dolan@latimes.com

lee.romney@latimes.com

Times staff writers Evan Halper, Shane Goldmacher, Esmeralda Bermudez and Ching-Ching Ni contributed to this report.