Justice Anthony Kennedy wrote the opinion for the court, which voted 7-2 to reverse a lower court's ruling.
Alliance Defending Freedom
The Arizona-based conservative legal organization has won five cases in the Supreme Court over the past three years.
Oral arguments in Masterpiece Cakeshop v. Colorado Civil Rights Commission will be heard Dec. 5.
The Newseum hosts a debate as the gay wedding cake case, Masterpiece Cake Shop vs. the Colorado Civil Rights Commission, case goes before the U.S. Supreme Court.