QUESTION: I think  I  understand that Congress can delegate its legislative  power to executive and administrative agencies, but cannot subsequently retract  it (Such a “legislative  veto” is  unconstitutional.  INS v.  Chadha).  We also talked about the exceptional conditions in which just one house  can act alone (impeachments, presidential elections,  treaty ratification,  etc.).  What I’m not sure of is what exactly Congress as a  whole CAN veto?
ANSWER: What matters is not whether Congress's action might be characterized as a "veto" -- a rejection of administration policy. What matters is whether Congress, when it acts to affect the rights and responsibilities of persons outside the legislative branch, has followed all of the requirements of the lawmaking process set out in Article I. That was the real (and only) problem in Chadha.