The US Supreme Court yesterday rejected an evangelical Christian minister's attempt to overturn California's ban on 'gay conversion' therapy aimed at turning youths under the age of 18 away from homosexuality.

Turning away a challenge to the 2012 law for the second time in three years, the justices let stand a lower court's ruling that it was constitutional and neither impinged upon free exercise of religion, as the minister claimed, nor impacted the activities of clergy members.

The law bans state-licensed mental health professionals, including psychologists and social workers, from offering therapy to change sexual orientation in minors.

In 2014, the Supreme Court in refused to review the law after an appeals court rejected claims that the ban infringed on free speech rights under the US Constitution's First Amendment.

California outlawed 'gay conversion' therapy in 2012, saying it was ineffective and harmful. New Jersey, Illinois, Oregon, Vermont, New Mexico and the District of Columbia have similar laws banning the practice, according to the pressure group Human Rights Campaign. The Supreme Court similarly rejected a challenge to New Jersey's law in 2015.

Gay conversion therapy methods include hypnosis and dating training as well as more extreme aversive techniques that induce pain or electric shocks in response to same-sex erotic images. California officials said in court papers that such treatments stem from a belief that homosexuality is a mental illness, which is a view that has been discredited for decades.

The lead plaintiff in the case was Donald Welch, an ordained minister and licensed family therapist based at the evangelical Skyline Wesleyan Church in the San Diego area. Welch sued the state along with a Catholic psychiatrist and a man who underwent conversion therapy and now aspires to perform it on others.