Flynn never directly said he would overturn the sanctions. Even the NYT said the situation was “ambiguous” enough where Trump could keep him. I did a whole post on the situation here:
http://www.freerepublic.com/focus/f-bloggers/3524661/posts
The issue wasn’t whether Flynn would overturn the sanctions. It was whether he’d discussed the sanctions. He said straight up that he had not. But he had; it was a lie.