President Trump declared a national emergency at the US-Mexico border Friday, February 15, in order to get the money he wants to build his promised border wall. The declaration, which was made in the White House Rose Garden to gathered reporters, will enable the president to access taxpayer money without Congressional approval — a move that’s being met with concern from politicians on both sides of the aisle.

“I’m going to be signing a national emergency,” the president said during his announcement, explaining his oft-cited and false claims of violent acts and drug trafficking at the southern border. “We’re talking about an invasion in our country with drugs, with human traffickers, with all types of criminals and gangs.”

The president said the funding for the wall will be siphoned from military building and counter-drug efforts to the tune of $8 billion — a number that combines the approved funding from Thursday’s omnibus spending bill with the extra repurposed funds.

With bipartisan pushback in Congress, the president’s plan may face several possible legal obstacles. William Banks, a national security law expert at Syracuse University, toldVox on Thursday that an arcane law may prevent the declaration from legally being enacted.

The law, called “Construction authority in the event of a declaration of war or national emergency,” states that the military must be used in any emergency building scenarios, and that only funding from military building expenditures not already earmarked may be used.

But, beyond the spending rules, the onus is on the president to prove that the military is the only group able to do the construction (a case that will prove to be rather difficult to make, especially considering that the US is not at war with Mexico), and that military spending is better utilized on the southern border than in active military engagements at home or abroad.

With a growing chorus of Republicans speaking out against the unorthodox move, the president’s declaration could be sowing the seeds of dissent among even his most fervent supporters. “I don’t think this is a matter that should be declared a national emergency,” Senator Lisa Murkowski said Friday morning. “We as legislators are trying to address the president’s priority. What we’re voting on now is perhaps an imperfect solution, but it’s one we could get consensus on.”

Senator Susan Collins warned such a declaration was “of dubious constitutionality,” while Senator Marco Rubio called it “a bad idea.” Senator Rand Paul (who has been vocally supportive of Trump in the past) explained that circumventing Congress blurs the lines of power, saying, “We have a government that has a Constitution that has a division of power, and revenue raising and spending power was given to Congress, [not the president].”

(Photo by Alex Wong/Getty Images)