* U.S. judge struck down gay marriage ban in California
* That judge then disclosed his own same-sex relationship
* Separate judge rejects attempt to toss ruling (Adds details of case, byline)
By Dan Levine and Peter Henderson
SAN FRANCISCO, June 14 (Reuters) - A U.S. judge's same-sex relationship is no reason to toss out his ruling backing same-sex matrimony, another federal judge ruled on Tuesday.
The decision by Chief U.S. District Judge James Ware backed the prior ruling overturning California's gay marriage ban.
U.S. District Judge Vaughn Walker in San Francisco last year struck down California's same-sex marriage ban, known as Proposition 8, and supporters of the ban now say his ruling was compromised and should be vacated.
The case was immediately appealed to the 9th U.S. Circuit Court of Appeals.
The case could set national policy if it reaches the U.S. Supreme Court and is being watched throughout the nation, where same-sex marriage is legal in only a handful of states.
In a written ruling on Tuesday, the Judge Ware said Walker's same-sex relationship was no reason to throw out his decision. Ware took over the case after Walker retired earlier this year.
"It is not reasonable to presume that a judge is incapable of making an impartial decision about the constitutionality of a law, solely because, as a citizen, the judge could be affected by the proceeding," Ware wrote.
Shortly after Walker retired, he discussed his homosexuality in the press for the first time, saying he is in a 10-year relationship with a physician.
The 9th Circuit is still considering the constitutional issues surrounding gay marriage, and it has asked the California Supreme Court to weigh in on one point of state law.
The case in U.S. District Court, Northern District of California is Perry v. Schwarzenegger, 09-2292. (Reporting by Dan Levine and Peter Henderson; editing by Christopher Wilson)