“Cake decorating is his medium for creating art and they are compelling him to engage in artistic expression that violates his beliefs,” Mr. Tedesco said, resulting in a trampling of his First Amendment rights to freedom of expression and religion.

But a unanimous three-judge panel of the Colorado Court of Appeals, in upholding the decision of the state Commission on Human Rights, rejected the argument that selling a cake to a gay couple was so great an infringement on Mr. Phillip’s beliefs that it trumped the anti-discrimination law.

No reasonable observer, the decision said, “would interpret Masterpiece’s providing a wedding cake for a same-sex couple as an endorsement of same-sex marriage, rather than a reflection of its desire to conduct business in accordance with Colorado’s public accommodations law.”