A Rancho San Diego pastor is among those suing to overturn a landmark law that prohibits licensed mental health professionals from applying therapies intended to make gay and lesbian youth straight.

Donald Welch, an ordained minister at Skyline Church, is challenging the legislation signed Saturday by Gov. Jerry Brown on the basis that it violates the First Amendment of the Constitution of the United States as well as equal protection rights, according to U-T San Diego.

The suit was filed Monday in U.S. District Court in Sacramento by the Sacramento Pacific Legal Institute on behalf of Welch and others, the newspaper reported.

Institute President Brad Dacus told U-T San Diego that the legislation combines psychiatric ignorance and political negligence while violating the rights of youths to seek counsel if they feel it is necessary.

Sen. Ted Lieu, D-Torrance, the legislation's author, told U-T San Diego that the lawsuit was "frivolous" and a stretch of free speech rights.

Conversion therapy "has no basis in medicine and, in fact, causes harm," which gives the state the authority to step in, he said.

Proponents of the law, which is scheduled to take effect Jan. 1, include medical and psychological groups as well as state and national gay rights advocates.

In addition to ministering at Skyline Church, Welch serves as an adjunct professor at Point Loma Nazarene and Azusa Pacific universities. He did not respond to phone calls or emails, U-T San Diego reported.