The bill passed both houses of the New Jersey Legislature with bipartisan support in June. Assemblyman Tim Eustace, who sponsored the bill and is openly gay, described the therapy as "an insidious form of child abuse."
In a note accompanying the bill, Christie said he believes people are born gay and that homosexuality is not a sin. That view is inconsistent with his Catholic faith, which teaches that homosexual acts are sins.
The Republican governor also said the health risks of trying to change a child's sexual orientation, as identified by the American Psychological Association, outweigh concerns over the government setting limits on parental choice.
"Government should tread carefully into this area," he said in the note, "and I do so here reluctantly."
"However, I also believe that on the issues of medical treatment for children we must look to experts in the field to determine the relative risks and rewards," Christie said, citing a litany of potential ill effects of trying to change sexual orientation, including depression and suicide. "I believe that exposing children to these health risks without clear evidence of benefits that outweigh these serious risks is not appropriate."
Gay rights activists applauded the ban but pushed for more.
"It is our truest hope that the governor will realize, as the majority of the legislature and a super-majority of the pubic have realized, that the best way to ensure lesbian, gay, bisexual, transgender youth are protected from the abuse of being ostracized is to provide them with equality," Troy Stevenson, executive director of the state's largest gay rights group, Garden State Equality, said in a statement.
Christie previously vetoed gay marriage legislation. He has said he supports the state's civil union law, which was enacted to give gay couples the benefits of marriage but not the title. Gay couples have since sued, claiming that the law provides unequal treatment to same-sex couples. Their lawyers say the U.S. Supreme Court ruling granting federal benefits to gay married couples strengthens their case in state court, while Christie administration lawyers say the federal government should recognize the state's civil union law as the equivalent to marriage. A trial court decision is expected next month.
Gay rights groups say the practice of conversion therapy is damaging to young people because it tells them that it's not acceptable to be whoever they are.
Some social conservatives framed the debate as a parental rights issue, saying a ban on the counseling would limit the ability of parents to do what they think is best for their children.
The idea of conversion therapy is an old one that has increasingly drawn criticism for its methods. Last year, four gay men sued a Jersey City group for fraud, saying its program included making them strip naked and attack effigies of their mothers with baseball bats.
Lawmakers heard horror stories from some during hearings on the ban, including Brielle Goldani of Toms River, who testified she underwent electric shocks and was given drugs to induce vomiting after being sent to an Ohio camp at age 14 to become straight.
But, they also heard from Tara King, a Brick-based counselor, who said she should be allowed to "fix" what patients, even under-aged clients, want fixed.