California and 15 other US states have filed a lawsuit against Donald Trump's emergency declaration to fund a wall on the US-Mexico border.
alifornia Attorney General Xavier Becerra released a statement saying the suit alleges Mr Trump's administration's action violates the US Constitution.
"President Trump treats the rule of law with utter contempt," Mr Becerra said.
"He knows there is no border crisis, he knows his emergency declaration is unwarranted, and he admits that he will likely lose this case in court."
Joining California in filing the lawsuit are the attorneys general of Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Michigan, Minnesota, Nevada, New Jersey, New Mexico, New York, Oregon, and Virginia.
Mr Trump declared a national emergency to fulfil his promise of completing the wall.
The move allows the president to bypass Congress to use money from the Pentagon and other budgets.
California has repeatedly challenged Mr Trump in court.
"President Trump is manufacturing a crisis and declaring a made-up 'national emergency' in order to seize power and undermine the Constitution," said California Governor Gavin Newsom in a statement.
"This 'emergency' is a national disgrace."