A federal appeals court last week told the group American Atheists to better explain how the Ground Zero Cross display at the National September 11 Memorial Museum, which opened last month, violates the constitutional rights of its members, who find it offensive.

A federal judge in the Southern District of New York last year threw out the group's lawsuit, filed in 2011 against the display of the 17-foot steel cross beam, which was found in the World Trade Center rubble following the Sept. 11 terror attacks, Fox News reported.

Before moving the cross out of the debris to make way for reconstruction, several first responders and crew used it as a sort of shrine. It has become a tourist attraction.

In its ruling Thursday, the appeals court cited an amicus brief filed by the Becket Fund for Religious Liberty, a nonprofit law firm specializing in church-state law and the protection of religious expression.

Becket lawyer Eric Baxter said the brief argues that the atheists group doesn't have the right to sue.

"We're thrilled that the court picked up on this issue," Baxter said. "Courts should not allow people to sue just because they claim to get 'dyspepsia' over a historical artifact displayed in a museum."

American Atheists must file supplemental legal briefs by July 14 so the judge can decide whether or not to proceed with the case. The group must explain how the offensiveness of the cross is a "constitutional injury," according to Fox.

Group members must also explain how the cross display, which they say "marginalizes them as American citizens," is a "particular and concrete injury" rather than just "the abstract stigmatization of atheists generally."

"Taking personal offense is not an injury that warrants invoking the power of the courts to shut down everything you disagree with," Baxter said. "The Constitution is not a personal tool for censoring everyone's beliefs but your own."

The judge also told the group to substantiate its claim that the museum and memorial are receiving tax money.