Explain how if congress rejects a bill that the president can veto it. If it is not sent to the president’s desk as a piece of legislation, there is nothing to veto.
Some people on Free Republic started this rumor that the president can veto a negative vote by congress and people like you have picked up on it.
It can’t happen. Not even under Obama.
Hmmm...... so the agreement is not a treaty
then the congressional product is not a vetoable bill but a vote of no confidence, a condemnation, a censorship
For your reading pleasure:http://www.vox.com/2015/4/15/8420669/corker-menendez-iran-sanctions
He won't 'veto the veto'. He'll merely follow the agreement to the letter without congressional approval.
Who will stop him?