President Donald Trump's declaration of an emergency Friday to build a border wall immediately drew legal challenges that could easily escalate into a landmark test of the balance of power between the White House and Congress.
Legal experts said it was "unprecedented" for a president to use his emergency powers to overcome Congress's refusal to fund his wishes, in this case a barrier on the US-Mexican border to keep out illegal immigrants.
They also questioned Trump's categorization of the immigration issue as a national emergency and his tapping military funds for a non-military project.
Hours after the announcement, the Trump administration faced an investigation by the House Judiciary committee and lawsuits from New York, California and the American Civil Liberties Union.
"President Trump is manufacturing a crisis and declaring a made-up 'national emergency' in order to seize power and subvert the constitution," said California Governor Gavin Newsome.
"California will see you in court."
Trump said he expected a legal fight and predicted he would prevail.
"We will have a national emergency, and we will then be sued," Trump said Friday.
"Then we will end up in the Supreme Court, and hopefully we will get a fair shake, and we'll win in the Supreme Court."