The justices by a 6-3 vote sided with a graphic artist in Colorado who said she wants to expand her business to design custom websites that celebrate impending marriages, but not for same-sex couples. She cited her belief as a Christian that marriage is limited to a man and a woman.

“The 1st Amendment prohibits Colorado from forcing a website designer to create expressive designs speaking messages with which the designer disagrees,” Justice Neil M. Gorsuch wrote in the majority opinion.

Lorie Smith, the graphic artist, sued Colorado in federal court and sought a 1st Amendment ruling that would protect her freedom of speech which — her attorneys noted — included the right not to speak.

In ruling for her in the case of 303 Creative vs. Elenis, the high court said the Constitution’s protection for free expression outweighs the state’s authority to require that businesses open to the public provide equal service to all.

The court’s six conservatives, all of them Republican appointees, were in the majority and the three liberals appointed by Democrats were in dissent.

Justice Sonia Sotomayor said in her dissent that “the court, for the first time in its history, grants a business open to the public a constitutional right to refuse to serve members of a protected class.”

But the ruling was limited to matters of speech and expression, and it does not appear to create a broad right for businesses or stores to discriminate based on sexual orientation.

The court’s opinion does not affect its 2015 ruling that same-sex couples have a constitutional right to marry and to have their unions treated equally under the law.

It does, however, create an exception to that principle of equal rights. It permits some business owners to turn away same-sex couples if the service or product at issue involves speech or creative expression that celebrates their marriage.

The ruling is a victory for conservative Christians and the Arizona-based Alliance Defending Freedom, which has repeatedly gone to court on behalf of wedding photographers, cake makers, florists and other “artists” who said it would violate their religious beliefs and their right to free expression to be required to participate — even indirectly — in a same-sex marriage.

The decision is a setback for the gay rights movement and for LGBTQ+ customers who could face more discrimination, particularly when planning a wedding.