I don't think there are any enforcable legal consequences.
First, we have a powerful argument that the sanctions were imposed against the previous regiem. They are no longer in effect, Iraq is a different country than a month ago. We just go ahead and start shipping oil.
Secondly, the UN couldn't keep Iraq from cheating on the embargo. Which country would be willing to stop a tanker bound for the US? The UN has no navy of its own.
Big advantage--we again get to demonstrate that the UN is irrelevant.