The Rev. Frank Schaefer, pastor of the Zion United Methodist Church of Iona in Lebanon County, could be reprimanded, suspended or be stripped of his ministry, The Philadelphia Inquirer reported.
The jury of fellow pastors reached its conclusion Monday night after a one-day trial at a retreat center in Spring City.
Dozens of church members and others sang hymns and other songs while waiting in line for the proceeding to start, the newspaper said. Some carried signs in support of Schaefer. "Love casts out fear," one read.
"Most of our congregation is straight," said Beverly Rainforth, 64, one of several people who traveled to Pennsylvania from Binghamton, N.Y., where the pastor of another Methodist church faces a similar complaint. "We just believe this is a really important social issue."
Former church member Jon Boger brought the accusation against Schaefer, who conducted the marriage ceremony in Boston in 2007.
Schaefer did not dispute that he performed the wedding but said he did so to show love and respect to all human beings in accordance with his teachings.
"Maybe I've compromised my ritual purity, but I believe that's what Jesus called me to do," he told the jurors.
Boger, who brought the complaint against Schaefer in April, said the rumors that Schaefer conducted a gay marriage bothered him and undermined the church's integrity.
"It was a lie and a broken covenant," Boger testified. "When I see him, I see a clerical collar with a shatter across it."
Boger acknowledged his mother, the longtime choir director at the church, had serious disagreements with Schaefer, but said that was unrelated to his decision to bring the complaint.
Schaefer's trial is the first in the church since the U.S. Supreme Court struck down the Defense of Marriage Act, the newspaper said.
The United Methodist Church, which has 12 million members worldwide, accepts gay members, but its doctrine prohibits same-sex marriage.
Dozens of United Methodist pastors from eastern Pennsylvania have shown solidarity with Schaefer by presiding over a recent same-sex union in a Philadelphia church, the newspaper noted.