Rep. Adam Schiff (D-Calif.) had a blunt assessment after President Donald Trump doubled down on his threat to declare a national emergency in order to build his border wall: Trump “doesn’t have the power.”

Before leaving for Camp David on Sunday, the president told reporters that he was considering using emergency powers to build a wall on the southern border, the funding for which Congress has refused to provide. The government has been partially shut down over this impasse.

Schiff, the incoming chairman of the House intelligence committee, told CNN’s Jake Tapper that not only is that rhetoric “really threatening,” but suggested that the president can’t even do that.

“If Harry Truman couldn’t nationalize the steel industry during wartime, this president doesn’t have the power to declare an emergency and build a multibillion-dollar wall on the border,” Schiff said on Tapper’s “State of the Union” Sunday. “So that’s a nonstarter.”

Truman had cited a national emergency during the Korean War to take control of the steel industry in 1952, but the U.S. Supreme Court struck down his executive order.

Trump’s government shutdown has hinged on his demand for more than $5 billion in wall funding, but neither the president nor the newly empowered Democrats in the House of Representatives seem to be budging.

Trump first floated the national emergency idea during a press conference Friday, but whether he can actually do so is a gray area, legal experts told NBC News.

“He can declare some kind of national emergency, but what it would allow him to do legally is a totally different question,” George Washington University professor and presidential power expert Matt Dallek told the outlet.

Harvard Law School professor Mark Tushnet told NBC that Trump may actually be able to get his wall by turning to certain unused Defense Department funds that Congress doles out yearly with no specific intention.

“My instinct is to say that if he declares a national emergency and uses this pot of unappropriated money for the wall, he’s on very solid legal ground,” Tushnet said.

GOP and Democratic leaders have met multiple times to negotiate an end to the government shutdown, which went into effect Dec. 21, but acting White House chief of staff Mick Mulvaney says little progress has been made.