Elizabeth Goitein:

So, there are two questions. The first is, can he declare the emergency? And, as we discussed, under the National Emergency Act, it's very easy for him to do that.

And, frankly, even if there isn't a real emergency, there are very few judges who are going to actually try to look behind that determination.

But a national emergency doesn't mean that he can do anything he wants. He is still limited to those specific powers that Congress has — has specified in, granted, a lot of different laws. So, the question is, are there specific laws in there that would allow him to build the wall?

And there are a couple of laws that do allow the president to move money around within the Department of Defense for military construction projects or civil defense projects. And I'm sure those are the powers that the White House lawyers and the Department of Defense lawyers are looking at very closely right now.