One can certainly imagine a set of circumstances under which a government official came to possess valuable corporate information. For instance, a Customs official searching an investment banker might learn of a merger in the works. Acting on that insider information would already be illegal. Violating a nondisclosure agreement wouldn't add too much to the guy's troubles if he were caught!
I wonder if anything like that has ever happened? The answer is probably yes, but I just never heard of such a case.
Bruce