While Democrats are preparing to propose a joint resolution challenging President Donald Trump's national emergency declaration in order to obtain funding for a border wall, one legal scholar is among those arguing the time has come to pursue a far more direct and effective method of combating the president's lawlessness: impeachment.

Ahead of Trump's national emergency declaration Friday morning, international law professor Francis Boyle said there is no time to lose.

"This should be initiated immediately," said Boyle. "All you need is one brave member of the U.S. House of Representatives to meaningfully assert that body's Power of the Purse. Trump's indications that he will override that legislative power and the seeming acquiescence by some Democrats is illegitimate and dangerous and subverts a fundamental premise of the Constitution.

Boyle—who worked closely with former Rep. Henry Gonzalez (D-Texas) to introduce a resolution to impeach President George H.W. Bush for high crimes and misdemeanors after he initiated the first Gulf War—said Congress has a solid case for bringing charges against Trump over his violation of the U.S. Constitution:

A Bill of Impeachment could consist of articles including for (1) violating Article 1, Section 7 of the United States Constitution: "All Bills for raising Revenue shall originate in the House of Representatives…" (2) Article 1, Section 8 of the Constitution: "No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law…" (3) It also violates the Federal Anti-Deficiency Statute.

With Trump preparing to unilaterally take control of government funds by declaring a national emergency, Boyle said, lawmakers' "most direct remedy is impeachment."

Journalist John Nichols, who has advocated for impeachment as "the cure for a constitutional crisis," was among those who agreed with Boyle on social media, arguing that the U.S. is indeed in a state of national emergency as Trump has claimed—just not an emergency that will be fixed with a wall at the U.S.-Mexico border.

"President Trump's illegal declaration of a national emergency to build a wall on the southern border of the United States that Congress has not authorized is a clear abuse of power," said John Bonifaz, president of the pro-democracy group Free Speech For People, in a statement.  "It is time—long past time—for members of the U.S. House of Representatives to carry out their constitutional responsibilities and to start impeachment proceedings now against this president.  We cannot continue to have a lawless president in the White House."

Peter Gleick, a climate scientist and advocate for impeachment, wrote on Twitter Thursday evening that looking back at the Trump administration, future generations will likely be baffled if lawmakers fail to impeach the president.