A wedding cake with a male couple is seen at The Abbey restaurant at a celebration of the over100 same-sex marriages performed today in West Hollywood, California, July 1 2013.. The U.S. Ninth Circuit Court of Appeals lifted California's ban on same-sex marriages just three days after the Supreme Court ruled that supporters of the ban, Proposition 8, could not defend it before the high court. AFP PHOTO / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
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A wedding cake with a male couple is seen at The Abbey restaurant at a celebration of the over100 same-sex marriages performed today in West Hollywood, California, July 1 2013.. The U.S. Ninth Circuit Court of Appeals lifted California's ban on same-sex marriages just three days after the Supreme Court ruled that supporters of the ban, Proposition 8, could not defend it before the high court. AFP PHOTO / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
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(CNN) —  

The Trump administration is backing a Colorado baker who refused to create a cake for the wedding of a same-sex couple.

The case – one of the most important to be heard this term – pits advocates for religious liberty against supporters of LGBT rights.

In a friend-of-the-court brief filed with the Supreme Court, the Justice Department urged the court to side with Masterpiece Cakeshop owner Jack Phillips, who says making a cake for a same-sex couple violates his religious liberty.

“Forcing Phillips to create expression for and participate in a ceremony that violates his sincerely held religious beliefs invades his First Amendment rights,” Acting Solicitor General Jeff Wall wrote for the Justice Department.

“The government may not enact content-based laws commanding a speaker to engage in protected expression: An artist cannot be forced to paint, a musician cannot be forced to play, and a poet cannot be forced to write,” the brief adds.

The case dates back to 2012, when David Mullins and Charlie Craig asked Phillips to create a cake to celebrate their wedding. Phillips refused, citing religious objections. Lower courts, citing a state anti-discrimination law, ruled in favor of the couple.

The filing by the government is significant, in part, as it indicates the difference between the two administrations. The Obama administration would not have filed such a brief. The United States is not an official party to the case, and it was Wall’s choice to file.

“It’s not unusual for the federal government to file an amicus brief in such an important constitutional case,” said Steve Vladeck, CNN Supreme Court analyst and professor at the University of Texas School of Law.

“What makes this brief unusual is its substance. It’s practically unheard of for the Justice Department to argue in favor of a constitutional exemption to antidiscrimination laws – a constitutional right to discriminate. But that’s exactly what this brief is doing,” Vladeck said.

Justice Department spokesperson Lauren Ehrsam said the filing emphasizes that the “First Amendment protects the right of free expression for all Americans.

Although public-accommodations laws serve important purposes, they – like other laws – must yield to the individual freedoms that the First Amendment guarantees. That includes the freedom not to create expression for ceremonies that violate one’s religious beliefs.”

The ACLU, which is representing the couple, responded with a statement blasting the administration.

“This Justice Department has already made its hostility to the rights of LGBT people and so many others crystal clear,” said Louise Melling, ACLU’s deputy legal director. “But this brief was shocking, even for this administration. What the Trump Administration is advocating for is nothing short of a constitutional right to discriminate.”