Four men, including the now 33-year-old Ferguson, sued the group in 2012 under New Jersey's consumer-fraud laws.
Attorneys for the plaintiffs argued during the trial that JONAH claimed a success rate that wasn't backed up by actual statistics and used therapy methods that had no scientific basis, including having one client beat a pillow, meant to represent his mother, with a tennis racket.
"This is a momentous event in the history of LGBT rights," attorney David Dinielli said. "The same lies that motivate gay conversion therapy motivate homophobia — that gay people are broken and need to be fixed. The strength of our plaintiffs brought that to light."
Defense attorney Charles LiMandri argued that JONAH didn't make guarantees and should be allowed to offer help to people struggling with their sexuality. He also said none of the plaintiffs complained about the therapy during or immediately after participating in it and sued only after connecting with activists who wanted to shut down JONAH.
Ferguson sought help from JONAH at age 26 at the suggestion of his Mormon bishop and after undergoing counseling while a student at Brigham Young University. He spent eight months at JONAH's New Jersey center and said Thursday the trial took its toll.
"It's been grueling," he said. "I literally had a panic attack from having to relive the abuse that I went through at the hands of JONAH and JONAH counselors."
Ferguson credits the seeds of his Mormon faith, including the singing of familiar LDS hymns — "Faith in Every Footstep" and "Do What Is Right" — with helping him navigate the trial's emotional roller coaster.
"It's ironic," he said, "that the principles the LDS Church gave me are how I maintained the strength and courage to overcome the lies of conversion therapy.
In December 2013, Ferguson married Seth Anderson, becoming the first same-sex couple to legally wed in Utah.
LDS leaders teach that same-sex attraction itself is not a sin, but acting on it is. The Church of Jesus Christ of Latter-day Saints does not officially endorse conversion therapy, although in the past it had ties to organizations that included the practice as a counseling or treatment option.
Thursday's decision was the first by a court to rule that conversion therapy practices are unconscionable and fraudulent, said Ferguson's attorney, Sam Wolfe of the Southern Poverty Law Center.
The original four plaintiffs — Ferguson and three men from Orthodox Jewish families — alleged the nonprofit exploited them with false promises as they struggled with their same-sex attractions in strict religious environments where they were expected to marry women and have children.
The trial began in early June and featured testimony from the men about the group's methods, which they said included engaging in role play that involved a locker room scene where gay slurs were used. JONAH presented witnesses who said the therapy helped them overcome their same-sex attractions.
Goldberg acknowledged during cross-examination that the group claimed a "success" rate of 65 percent to 75 percent to turn gay men to straight even though it didn't keep its own statistics and relied on anecdotal evidence from counselors.