Phillips’s lawyers say that analysis doesn’t give enough weight to the creativity and expression that goes into each of his cakes.

"Much like an artist sketching on canvas or a sculptor using clay, Phillips meticulously crafts each wedding cake through hours of sketching, sculpting, and hand-painting," his lawyers at the advocacy group Alliance Defending Freedom argued in court papers. The cake "announces through Phillips’s voice that a marriage has occurred and should be celebrated."

Phillips’s team points to a unanimous 1995 Supreme Court decision that said a Boston veterans’ group had a First Amendment right not to open its St. Patrick’s Day parade to an Irish-American gay-rights organization.

Bar Mitzvahs

Lawyers at the American Civil Liberties Union, representing Craig and Mullins, say the Supreme Court has consistently ruled that businesses don’t have a constitutional right to discriminate.

The men’s lawyers say a ruling for Phillips would let bakeries refuse to make cakes for a bar mitzvah, an interracial couple’s wedding or a woman’s business school graduation party.

"There is no doubt that the bakery owner’s religious objections are sincere, but granting such a religious-based exemption would allow every business owner ‘to become a law unto himself,’" the legal team argued in court papers, quoting from an 1878 case. The Colorado Civil Rights Commission will also be arguing on the side of the two men.

Although Phillips is also making a religious-rights claim, many legal experts say they expect free speech to be the focus of the argument.

‘Inherently Expressive’

That’s in part because of a Trump administration brief that urges a limited free-speech ruling in favor of Phillips. The administration says the First Amendment protects bakers, musicians, photographers and other wedding vendors who make "inherently expressive products," letting them decline to create custom products for same-sex weddings.