Bruce Ackerman, a professor of law at Yale, explains how illegal Trump’s plan to use emergency powers to build Wall would be. Trump’s plan is to take military funding to pay for Wall, and use the military to build it.

While it is hard to know exactly what the president has in mind, or whether he has any conception about what it would entail, one thing is clear: Not only would such an action be illegal, but if members of the armed forces obeyed his command, they would be committing a federal crime.

There are laws against it.

In response to the Hurricane Katrina disaster in New Orleans, Congress created an express exception to the rules, and authorized the military to play a backup role in “major public emergencies.” But in 2008 Congress and President Bush repealed this sweeping exception. Is President Trump aware of this express repudiation of the power which he is threatening to invoke?

But, Trump would say, they’re terrorists.

It is, I suppose, possible to imagine a situation in which the president might take advantage of the most recent exception, enacted in 2011, which authorized the military detention of suspected terrorists associated with Al Qaeda or the Taliban. But despite President Trump’s unsupported claims about “terrorists” trying to cross the border, it is an unconscionable stretch to use this proviso to support using the military for operations against the desperate refugees from Central America seeking asylum in our country.

There could be terrorists (or a terrorist) among them, just as there could be terrorists anywhere else. But we don’t imprison the whole population because who knows, there might be terrorists or school shooters among them, so why would be unleash the military on refugees because there might be terrorists among them?

The law is clear; how it would play out is less so. But undoubtedly, we would see a period of passionate debate on Capitol Hill, with scores of representatives, from both parties, condemning the president’s move as an unconstitutional abuse of his powers as commander in chief.

This would play out in public, with millions of service members watching closely. They would immediately be obliged to decide whether to obey President Trump — and risk criminal punishment. For the president to put these men and women in such a position, simply out of petulance over congressional opposition, would be especially unconscionable.

…

What this all adds up to is a potential crisis much graver than whatever immigration emergencies the president has in mind: A legally ignorant president forcing our troops to choose between his commands and the rule of law in a petty political struggle over a domestic political question.

Let’s hope he doesn’t step over the brink.