The U.S. Supreme Court on Monday ended the first legal challenge to a Republican-backed Mississippi law that permits businesses and government employees to refuse to serve lesbian, gay, bisexual and transgender people because of their religious beliefs.

The justices left in place a June ruling by the New Orleans-based 5th U.S. Circuit Court of Appeals that the plaintiffs - same-sex couples, civil rights advocates including the head of the state NAACP chapter, a church and others - did not have legal standing to bring the lawsuit.

The law, passed by the Republican-controlled state legislature and signed by Republican Governor Phillip Bryant with the backing of conservative Christian activists, has not yet been implemented and more legal challenges are expected, according to gay rights lawyers.

People who are refused service once the law is in place may be more likely to be judged to have legal standing to sue.

The 2016 law was passed in the aftermath of the U.S. Supreme Court's landmark 2015 ruling legalizing same-sex marriage nationwide.

Supporters call it a religious liberty law that protects the sincerely held religious beliefs and moral convictions of individuals and businesses. Opponents said it authorizes discrimination against LGBT people in violation of the U.S. Constitution's guarantees of equal protection under the law and the separation of church and state.

Mississippi's law was one of a series of measures proposed in socially conservative, Republican-dominated states that gay rights advocates viewed as an attempt to undermine the high court's gay marriage ruling.

(Reporting by Lawrence Hurley; Editing by Alistair Bell and Grant McCool)