> the U.S. federal government keeps interstate trade That's part of it, but there's actually also a set of interstate compacts (that still have to be "allowed"

> the U.S. federal government keeps interstate trade That's part of it, but there's actually also a set of interstate compacts (that still have to be "allowed" by Congress constitutionally) and also Uniform Codes (which don't). Particularly the uniform commercial code https://en.wikipedia.org/wiki/Uniform_Commercial_Code https://en.wikipedia.org/wiki/Uniform_Commercial_Code Basically, a think tank from the 50's decided to convince all the states to pass laws which just all happened to look alike because they copied from the same source. No interstate agreement required, they just all did it, no congressional thumbs up required. I... don't think the EU is quite on that level of unity yet =)