Trump is already being sued over his emergency declaration

Carlos Barria/Reuters

President Donald Trump declares a national emergency at the US-Mexico border as he speaks about border security in the Rose Garden of the White House in Washington on February 15, 2019.

• A watchdog group has already filed a lawsuit regarding President Donald Trump's national emergency declaration to build the border wall.
• The group is seeking to receive documents relating to the preparation of the declaration from the Justice Department.

A Washington-based government watchdog group has already filed a lawsuit against President Donald Trump's national emergency declaration to build physical barriers on the United States border with Mexico, becoming the first of what is likely to be many legal challenges to the president's unilateral action.

The Citizens for Responsibility and Ethics in Washington (CREW) filed a lawsuit Friday shortly after Trump's announcement demanding the Department of Justice's Office of Legal Counsel "provide documents concerning the legal authority of the president to invoke emergency powers..."

Read more: IT'S OFFICIAL: Trump declares national emergency to build his border wall

"Americans deserve to know the true basis for President Trump's unprecedented decision to enact emergency powers to pay for a border wall," CREW Executive Director Noah Bookbinder said in a statement. "We're suing because the government has so far failed produce the requested documents or provide an explanation for their delay."

CREW's lawsuit is seeking to have the Justice Department honor their January Freedom of Information Act request regarding documents showing "relevant communications, including legal opinions, from OLC, the Department of Homeland Security, and the Department of Defense" as they relate to Trump's previous threats to declare a national emergency.

The emergency declaration is already expected to face a litany of legal challenges.

Early Friday morning, ABC News reported the Justice Department had warned the White House about the prospect that his actions could be temporarily blocked by the courts.

Other prominent lawmakers - even those supporting Trump - have also questioned the president's legal authority to follow through with the declaration, which seeks to redirect certain appropriated funds to build an extension of the border wall.

Read more: Here's what you need to know about the border security compromise that could avert another government shutdown

But White House Acting Chief of Staff Mick Mulvaney brushed aside concerns that what the president was doing was in any way unprecedented during a conference call with reporters before the announcement.

"There's been some concern in the media about whether or not this creates a dangerous precedent," Mulvaney said. "It actually creates zero precedent. This is authority given to the president in the law already. It's not as if he just didn't get what he wanted so he's waving a magic wand and taking a bunch of money."

"I saw Nancy Pelosi said yesterday this sets a precedent for the Democrats to declare a gun emergency the next time they're in the Oval Office. That's completely false," he added. "If Democrats could've figured out a way to do it, they would have done that already."