ROFLMAO....
threatening to...leave the country....or 'do something illegal' ? Well, that sounds like sumpin' the Secret Service should (could?...nope)....IN ACCORD WITH LAW..."investigate". On the other hand....a proclamation which MIGHT be construed to be a "... threat to take the life of, to kidnap, or to inflict bodily harm upon the President of the United States" (18 USC Section 871) ?
Granted, 'moi' doubts Nugent was really "threatening" the life of Obama (with his diatribe). BUT, the LAW demands the Secret Service consider all such statements (when brought to their attention - which Nugent made..."easy") SERIOUSLY - requiring investigation to "rule-out. The Secret Service can (or at least before..."Columbia"...used to) get kinda testy about such things. L.