SACRAMENTO, Calif. — Gov. Jerry Brown has signed legislation prohibiting a form of therapy aimed at changing a minor’s sexual orientation from gay to straight, the first law of its kind in the nation, officials said Sunday.

State Sen. Ted Lieu, D-Torrance, introduced the measure based on his belief that so-called conversion therapy is non-scientific and dangerous because in some cases patients have later committed suicide or suffered severe mental and physical anguish.

“No one should stand idly by while children are being psychological abused, and anyone who forces a child to try to change their sexual orientation must understand this is unacceptable,” said Lieu. “Gov. Brown should be commended for protecting LGBT youth by ending this type of quackery.”

Kate Kendell, executive director of the National Center for Lesbian Rights, said the bill was needed so “state-licensed therapists cannot subject young people to practices that have been universally condemned by mainstream medical experts and that cause terrible harm.”

The bill was opposed by Republicans as an intrusion by the state into the decision of parents about how to raise their children.

The conservative Pacific Justice Institute, a California-based legal defense organization, has said it will file a lawsuit alleging that the measure violates constitutional protections, including the free speech rights of therapists and the right of patients to get access to information.

“The privacy concerns are fairly significant,” said Matthew B. McReynolds, a staff attorney for the institute. “In our view, it’s an intrusion beyond what the government has done before.”