"The thing that is particularly dangerous to look at are actions that, when they were done the first time, were seen as really aberrant and oddly sort of dangerous, that have become commonplace. Twenty-five years ago, shutting down the government for political brinkmanship was seen as absolutely crazy. It was someone no one would dare do. And now its routine.

"That's a sort of degeneration of norms. There's no law that says you can't do that. But the norms saying that that's something that is not acceptable have completely eroded. And now this is something that-it's just done as part of a process of political negotiation. It's almost become sort of a routine part of the system.

"I think that the law granting presidents the ability to assert emergency powers-it seems to me that this is a law that is incredibly permissive because there was a basic assumption that presidents would use it ways that were not for political gain, but were to actually address a problem that was an emergency.

"Like when President Carter used it to streamline action against Iran for taking hostages, or when President Bush used it in the aftermath of Hurricane Katrina. Those were not for political purposes. They were to respond quickly to a problem that needed a quick response. And the law, it seems, could potentially be used in the way President Trump is talking about using it. The reason it hasn't been before is because there was a norm saying this is actually for a real purpose, a real emergency. In this context, I think if it's used, basically as a sort off-ramp for political stalemate, that opens up a precedent to misuse this law even worse in the future."