[JasonC]

Of course they go. Congress delegates some decisions to trade reps to give them leverage negotiating with other countries. But how much is entirely up to the Congress, which can change trade laws any way they please anytime they please. Including withdrawing from any treaty they don't like. Every time Congress freely choses a policy some protectionist doesn't like, protectionists pretend they don't have the decision. Wrong, you just didn't win a debate within the Congress.

[hedgetrimmer]

But how much is entirely up to the Congress, which can change trade laws any way they please anytime they please

You "free traders" keep saying this. Our treaty obligations are making that impossible.