A protest against President Donald Trump in New York City on Monday.AFPJOHANNES EISELE  

Sixteen U.S. states sued President Donald Trump’s administration on Monday over his decision to declare a national emergency to fund a wall on the southern border with Mexico, saying the move violated the Constitution.

Mr. Trump announced the emergency on Friday in order to bypass Congress, which approved only a quarter of the $5.6 billion he wanted for the wall in a spending Bill.

But the lawsuit, filed in a federal court in California, said the President’s order was contrary to the Constitution’s presentment and appropriations clauses, which outline legislative procedures and define Congress as the final arbiter of public funds, respectively.

The move had already been announced by Xavier Becerra, the Attorney-General of California, who said on Sunday his State and others had legal standing because they risked losing moneys intended for military projects, disaster assistance and other purposes. Critics have warned that Mr. Trump has opened the door for future Presidents to call on the act whenever they fail to get their way with Congress. Should the States prevail, the case could work its way up to the Supreme Court, setting up a precedent-setting showdown on the separation of powers.

Seeking an injunction

California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Michigan, Minnesota, Nevada, New Jersey, New Mexico, New York, Oregon and Virginia are party to the complaint seeking an injunction.

The States “bring this action to protect their residents, natural resources, and economic interests from President Donald J. Trump’s flagrant disregard of fundamental separation of powers principles engrained in the United States Constitution,” the complaint said.

It added that Mr. Trump had veered the country toward a “constitutional crisis of his own making.” “Congress has repeatedly rebuffed the President’s insistence to fund a border wall, recently resulting in a record 35-day partial government shutdown over the border wall dispute,” it said.

“After the government reopened, Congress approved, and the President signed into law, a $1.375 billion appropriation for fencing along the southern border, but Congress made clear that funding could not be used to build President Trump’s proposed border wall.”

The complaint also questioned Mr. Trump’s categorisation of illegal border crossings as a national emergency, saying data issued by the administration refuted it. “Customs and Border Protection data show that unlawful entries are near 45-year lows,” it said.