The Rev. Art Cribbs, speaking to a small crowd of church members and supporters near the Pasadena Court building, said the wedding he performed May 23 would be his last until gay couples are given an equal right to marry.
"I have the support of most of the congregation," Cribbs said.
But he acknowledged that some of his flock were disappointed he would not be available to marry them or their children.
Calling his decision "personal and painful," Cribbs said he understood why some people say same-sex marriage is against their religious beliefs.
But with Proposition 8, he said, "a boundary has been crossed" between religion and civil law.
The state "failed to protect a vulnerable minority from the tyranny of a majority," Cribbs said.
"Our church is involved in justice issues, we are against discrimination," he said. "I personally have known the pain of rejection."
Three years ago, the San Marino church became an "open and affirming" congregation, welcoming same-sex unions, said church trustee Holy Burns.
Cribbs, who performed about 70 weddings a year, said he was never asked to preside over a same-sex wedding during the "short time" they were legal.
Supporters attending the news conference included the Rev. Susan Russell from All Saints Episcopal Church in Pasadena, where the first gay wedding ceremonies in the city were performed last year.
"I stand in solidarity (with) this profound stand for justice," said Russell, president of Integrity USA, the 30-year-old advocacy organization for the gay, lesbian, bisexual and transgender communities.
No one, she said, has the right to insert religious beliefs into the state Constitution.
"Liberty and justice for all should really mean all," Russell said.
Cribbs said he was simply following his conscience by refusing to marry couples until gay marriage is legal again. But he will continue to provide pre-marital counselling. A list of ministers willing to conduct ceremonies in his place is available to his congregation, he said.
Elsa Seifert, a member of the Altadena Community United Church of Christ, said she and her pastor, Joe McGowan, came to support Cribbs' position.
Legally, Seifert said, she's not sure what should be done to overturn Proposition 8.
"But I do know that protests can help," she said.