Donald Trump just slapped his old pal Steve Bannon with a cease and desist letter
The legal basis for the action is that Bannon violated his non-disclosure agreement. That seems like a weak case to me, since Bannon is talking about the commission of crimes, which can't be covered up by a civil contract.
In 2001, the Supreme Court found a "nondisclosure agreement not binding in respect to criminal activity."
In fact, Bannon would probably be committing a crime if he did NOT reveal what he knew about criminal activities. If he received monetary compensation with the understanding that he would hide criminal activity as part of the non-disclosure agreement, he may have committed several crimes already.