A national group that includes atheists and agnostics is objecting to Mississippi’s new standard license plate design that has the phrase “In God We Trust.”

The American Humanist Association sent a letter Thursday to the state’s revenue commissioner and attorney general. It demands that Mississippi either set a new standard license plate design without a religious phrase or allow people to get another license plate design without paying an extra fee.

The association says it could sue Mississippi if the change is not made.

“Mississippi’s law violates the First Amendment rights of atheists in accordance with firmly settled Supreme Court precedent,” American Humanist Association attorney Monica Miller said in a news release. “The Supreme Court has made clear that the state cannot force motorists to display an ideological message they deem unacceptable on their license plates.”

Revenue Commissioner Herb Frierson said Thursday he’s asking lawyers to review the letter. Frierson said the design was chosen by a commission that included representatives from the governor’s office, the state Department of Revenue, the attorney general’s office and the treasurer’s office.

The new standard license plate has been sold since January. The center shows the state seal, which includes “In God We Trust.”

Mississippi offers several specialty license plate designs for $30 extra per year.

The American Humanist Association’s letter to Mississippi officials cites a 1977 U.S. Supreme Court ruling in a dispute over the phrase “Live Free or Die” on New Hampshire’s standard license plate. People who were Jehovah’s Witnesses sued the state, saying the phrase was “repugnant to their moral, religious and political beliefs.”

The Supreme Court ruled that a state cannot force a person, as part of daily life, to display a phrase that violates their beliefs. Justices said the First Amendment protects “both the right to speak freely and the right to refrain from speaking at all.”