"Out of respect and out of honor of his commitment to his family, he's done this," said the Rev. Robin Hynicka of Philadelphia's Arch Street United Methodist Church, where the meeting was held. "Talk about family values, right. Let's give it its due."
The United Methodist church has about 12 million members worldwide. Church doctrine accepts homosexual members while barring openly gay pastors and the blessing of same-sex unions.
About a half-dozen people have been put on trial for breaking those rules since 2000, mostly in North America. Several trials ended with ministers being removed from their posts.
Heather Warren, an associate professor of religious studies at the University of Virginia, said the Methodist Church has a growing number of pro-gay members but was still more divided than other denominations, such as the Episcopal Church or United Church of Christ.
"Definitely in comparison to some of the other mainline churches, it is still more polarized," she said, adding that the debate often plays out through trials or at individual churches that have committed to promoting gay rights rather than on an international level.
Schaefer's trial, at a retreat house in the borough of Spring City, will be the first in the church since the U.S. Supreme Court struck down the Defense of Marriage Act. He knows the international Methodist community is watching intently.
"Once again society is bringing this to the church as a challenge," he said.
The 31 pastors committed to the group ceremony come from about 25 churches in Eastern Pennsylvania, from Lancaster to Reading to Philadelphia, according to the Rev. David Brown, also of Arch Street United Methodist Church. Ten other ministers are considering joining, he said.
"The more we get, the harder it will be for the church - it's not impossible - the harder it will be to go after any one person to take away their orders," Brown said.
Schaefer, 51, pastor of the Zion United Methodist Church of Iona in Lebanon County, attended Thursday's meeting, but he says he won't take part in the marriage ceremony or help organize it.
Brown said all of the participating pastors intended to sign the marriage certificate, a gesture that would have more impact if the state recognized same-sex marriages as legal.
Most are members of churches that are a part of or considering joining the Reconciling United Methodists of Eastern Pennsylvania, a coalition of congregations advocating for gay rights. But Brown said he was not sure whether any had ever officiated at a same-sex wedding.
He has not.
Neither has Hynicka, a longtime supporter of gay rights who decided to take this step despite the risk of losing his job and the health care that his wife, who has lupus, needs.
"It's a greater risk for me to deny God's spirit working in the church and in these colleagues," he said. "That's a greater risk to not follow God's leading now than for me to lose access to my health care."
The group also plans to gather at the Spring City retreat center for Schaefer's trial. A jury of other pastors will hear the case over several days.
Schaefer doesn't plan to deny performing the ceremony. Instead, he will present a team of religious experts he hopes will prove that his decision upheld other church doctrines - namely that pastors should minister to at-risk teens who have contemplated suicide due to confusion over their sexuality.
Schaefer said Tim was one those kids. His son's story will be central to his defense.
"There might be, hopefully, parents in the jury box, pastors that are also parents. I can't imagine that they couldn't understand that what I did was an act that any father probably would do," Schaefer said. "But then you never know."
Schaefer said that as a teen, Tim prayed to be cured of his homosexuality and considered suicide when that didn't happen.
Even before going to seminary, Schaefer thought the church's doctrine would "be in trouble" if it was proved that homosexuality is genetic.
His son, he said, offered him that assurance.
"To me that was the ultimate proof at that moment. For heaven's sakes, he didn't choose this," Schaefer said at his office last week, his eyes raised to the ceiling and palms reached out, "He didn't want this."
Though he knew the possible consequences, Schaefer said he didn't hesitate when Tim, now 29, asked him to officiate.
At the afternoon ceremony at a restaurant overlooking a marina near Boston, Schaefer settled on pronouncing the couple married "in a holy union ratified by God."
"Those whom God has joined together," he said, "let no one put asunder."
At the time, Schaefer told his supervisors about the ceremony but not his congregation. Then and for nearly six years after, he said, officials took no disciplinary action.
But in April - 26 days before the church's six-year statute of limitations was set to expire - a member of his congregation filed a complaint with the Eastern Pennsylvania Conference of the United Methodist Church.
A spokeswoman from the conference last week declined to answer questions about why charges were filed now.
In a statement, Bishop Peggy Johnson, one of three Methodist bishops in Pennsylvania, said complaints are confidential.
"I am in prayer for all involved in this process, and I urge everyone to join me in lifting up in prayer each of the persons involved," she said.
Critics say Schaefer could have avoided a trial several ways, first by denying his son's request.
"Good parenting 101 is realizing that not everything that your child asks you to give him or her is necessarily always the best thing for them," said John Lomperis, a director at the Institute on Religion and Democracy, a conservative think-tank.
Church officials also offered to forgo a trial if Schaefer agreed never to officiate at another same-sex wedding.
Schaefer says he couldn't do that.
Three of his four children are gay.
"I couldn't truthfully say I will never do this again," he said.
The other pastors are still developing plans for next month's ceremony, although it will take place before Schaefer's trial, according to Hynicka.
He declined to name the couple out of concern for their privacy.
He said the names of the participating pastors also won't be released before the ceremony but will be made public when each signs the marriage certificate.
"It's a statement. It's a movement. But it's also a marriage ceremony that's going to celebrate the love of two people," Hynicka said. "And we want to maintain that integrity."