The only problem with your statement is that in the Union of States in America each State has its own laws/Constitution.
That hasn't been done away with and POTUS DJT is living evidence that
"We" can't do squat as far as making our laws and regulations for us as long as we have a strong , working FedGov/StateGov system.
Yeah, the US has treaties and international agreements/obligations, but so far nobody else makes the law.
And how do those protect against a central government that opens the borders?
I very much enjoy discussion of how the feds have usurped and abused power, and how that principle can extent to entitles like WTO, UN, etc. But I haven't the patience and this isn;t the place, so I will just concede defeat and declare you the winner of this debate.