[dragonwriter]

> If Trump issues an order that Congress didn't like, what could they do?

In terms of substantive, direct, responses (e.g., excluding retaliating against other Presidential initiatives and appointments), major notable options include:

(1) Expressly prohibit the things called for in the order by legislation (overriding a veto, of necessary);

(2) Sue the administration claiming the order violates existing (statute or Constitutional) law;

(3) Impeach and remove the President.