SAN FRANCISCO - The first word on whether California's same-sex marriage ban passes scrutiny under the U.S. Constitution is scheduled to come down Wednesday when a federal judge issues his ruling in a landmark case.

Chief U.S. District Judge Vaughn Walker has reached a decision on whether to uphold or overturn the voter-approved ban known as Proposition 8 and plans to publish his opinion in the afternoon, court spokeswoman Lynn Fuller said.

His verdict comes in response to a lawsuit brought by two same-sex couples and the city of San Francisco seeking to invalidate the law as an unlawful infringement on the civil rights of gay men and lesbians...