Nineteen former Republican representatives have filed a friend of the court brief backing a lawsuit that challenges Donald Trump’s unilateral decision to fund his border wall without the support of Congress.

The amicus brief, filed Thursday in the U.S. District Court for the Western District of Texas, supports a suit by Protect Democracy, a nonpartisan nonprofit challenging Trump’s declaration of a national emergency at the U.S. southern border in February and his demand for funding to erect a wall between the U.S. and Mexico.

“I could do the wall over a longer period of time ― I didn’t need to do this,” Trump said in a televised speech at the time. “But I’d rather do it much faster.”

The former GOP representatives filed the brief just after the Pentagon, under orders from Trump, informed Congress this week that it would redirect some $1.5 billion earmarked for retirement accounts, a missile defense system and the war in Afghanistan to pay for a section of the border wall. That’s on top of an earlier $1 billion wall commitment from the Pentagon.

“The separation of powers is fundamental to our democracy,” noted the amicus brief, adding that the Constitution gives Congress the authority to appropriate funds. “The president’s emergency declaration is an unconstitutional attempt” to usurp that power, and “would deprive Congress of its most basic constitutional duty,” the brief argued.

“The framers considered ‘the accumulation of all powers, legislative, executive, judiciary, in the same hands’ to be the ‘very definition of tyranny,’” the brief continued.

The two women and 17 men who filed the brief are from a range of states, including New Hampshire, Texas, Missouri, New Jersey, Maryland, Nebraska, New York, Vermont, Rhode Island, Arizona and South Carolina.

“As members of Congress, we took an oath to support and defend the Constitution—and we continue to live by that oath today,” Mickey Edwards, congressman for Oklahoma from 1977 to 1993, said in a statement to Newsweek.

The suit is one of a number challenging Trump’s decision to erect the border wall without congressional support. The House of Representative has also filed a lawsuit, and California is leading a coalition of 20 states in a lawsuit challenging Trump’s emergency declaration. The states presented arguments Friday in U.S. District Court in Oakland, California.

A Justice Department lawyer argued that Congress approved the Pentagon budget and did not explicitly note that funds could not be used for a border wall.