The friend-of-the-court brief supports a federal judge’s temporary restraining order that blocked implementation of the ban Friday. It was filed with the Ninth Circuit Court of Appeals, which is hearing the government’s request to reinstate Trump’s order.

“The executive order singling out and punishing Muslims is not only contrary to this nation’s founding principles, it violates the U.S. Constitution, which forbids discrimination on the basis of religion,” said Naomi Tsu, deputy legal director of the Southern Poverty Law Center.

“We urge the federal Court of Appeals for the Ninth Circuit to reject the government’s attempt to enforce this unconstitutional order.”

The brief argues that the executive order “is unsupported by fact and is instead motivated by religious animus.”

It notes that the government is required to treat people equally, no matter what religion, if any, they follow. “Ignoring this clear constitutional command, the government has singled out one religious group – Muslims – for official disfavor and maltreatment,” the filing states. “By instituting a wide-ranging, punishing ban on Muslim immigrants, the government runs roughshod over core First Amendment protections.”

The brief also notes: “The Executive Order is what President Trump promised all along: a ‘Muslim ban.’ No amount of rebranding can change that. People are excluded, detained, and deported for no reason other than their deity and preferred holy book. The Executive Order is an insult to the fundamental principles of religious freedom enshrined in our Constitution. It cannot stand – even for a day.”