For four days last week, the small beige Covenant Presbyterian Church on the outskirts of Napa was turned into a courtroom.

The Rev. Jane Spahr, 68, was on trial, accused of failing to “further the peace, unity and purity of the church” by marrying 16 gay and lesbian couples in 2008 when same-sex marriage was legal in California.

Her judges were six mostly white-haired Presbyterian elders, who sat at a table beneath a cross, listening intently to the proceedings.

Friday began once again with a prayer. Then James Jones, the moderator of the judicial commission, stood and declared Ms. Spahr guilty of most of the charges. “We determine that you are hereby censured by rebuke,” Mr. Jones said. “You are enjoined to avoid such offenses in the future.”