“Probably the best evidence is the president’s own words,” said Becerra.

But it could be an uphill battle, as the National Emergencies Act offers no explicit definition or required conditions that must be met for the president to declare a crisis. As the Washington Post has pointed out, lawsuits over a president’s national emergency declaration have historically been rare and, with one exception, have generally failed.

Legal analysts say another hurdle for the plaintiffs is to show they have “standing” to sue, which requires them to identify how Trump’s actions could harm them. That is relatively straightforward for landowners or advocates for communities and wildlife in areas along the southwest border, where the wall is supposed to be built. But of the 16 states named in the suit filed Monday, only two — California and New Mexico — share a border with Mexico. The others, all of which except Maryland have Democratic governors, include Hawaii, Oregon, Illinois, Minnesota, New York and Virginia.

Based on the complaint, the suit seeks to argue that Trump’s unilateral redirection of federal funds for his border wall will have harmful economic impact on these states regardless of their proximity to the border.

“Plaintiff States collectively stand to lose millions in federal funding that their National Guard units receive for domestic drug interdiction and counter-drug activities, and millions of dollars received on an annual basis for law enforcement programs from the Treasury Forfeiture Fund, harming the public safety of Plaintiff States,” the complaint reads.

Another route to blocking the declaration runs through Congress, which can pass a resolution to overturn it, a option leading Democrats in the House have floated. But it would also have to pass the Republican-controlled Senate, and could be vetoed by the president, requiring a two-thirds majority in both houses to overturn — a very high hurdle.

The federal courts, including those under the Ninth Circuit, have been a thorn in Trump’s side since the start of his presidency. Advocacy groups such as the ACLU and others have successfully called on judges to block the implementation of several of Trump’s immigration policies, from the first iteration of the travel ban to the termination of DACA and Temporary Protected Status for several countries, to a policy severely restricting access to asylum for people who enter the country at the southwest border. While the courts, especially the Ninth Circuit, are often maligned by Trump as hotbeds of Democratic activism, some of the decisions that went against him were by judges appointed by Republican presidents. It was Judge Dana Sabraw, a George W. Bush appointee to the Ninth Circuit, who ordered the government to promptly track down and reunite thousands of parents and children it had forcibly separated under the administration’s zero-tolerance policy.

In his own stream-of-consciousness analysis of how this will all play out, Trump expressed hope that he would ultimately be victorious if given the chance to defend his emergency declaration at the Supreme Court, noting the high court’s favorable ruling in the travel ban case.

“I think what will happen is, sadly we’ll be sued, and sadly it’ll go through a process and happily we’ll win, I think,” he said Friday.

ooo