SAN FRANCISCO — A federal judge in San Francisco has reached a decision in a landmark case on whether California’s same-sex marriage ban violates the constitutional rights of gay men and lesbians.

Chief U.S. District Judge Vaughn Walker will issue his ruling today, said Lynn Fuller, a U.S. District Court spokeswoman.

The decision came in a lawsuit brought by two same-sex couples seeking to overturn California’s voter-approved Proposition 8, which outlaws gay marriage.

Both sides previously said an appeal was certain if Walker did not rule in their favor. The case would go first to the 9th U.S. Circuit Court of Appeals then the Supreme Court if the high court justices agree to review it.

Walker presided over a 13-day trial on the issue.