SAN FRANCISCO • U.S. District Judge Vaughn Walker kept same-sex marriages on hold in California for at least another week Thursday but suggested that top state officials' support for same-sex 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.

The defendants in the case were Gov. Arnold Schwarzenegger and Attorney General Jerry Brown. As the losing parties, they have authority to appeal Walker's ruling. But Brown and Schwarzenegger have hailed Walker's decision and said they would not appeal. A spokesman for Schwarzenegger repeated that position 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.

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

Several outside legal experts have voiced a similar opinion.

"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 standing, they would make no decision on the merits of the issue.