To prevail in a lawsuit the USPS would have to prove damages. What are its monetary damage? None of his former sponsors have a case.
Armstrong is an ahole, but that is a different issue.
He will have liability to those he defamed and to the media outlet he successfully sued for defamation.
In the world of cycling, his actions were nothing out of the ordinary, he just avoided getting caught longer than most.
And for the "also rans", they weren't even given the time of day........
It should also be mentioned that for a guy who was a doped up superman, he's not even in the top 25 of TDF stage winners so what were THEY on......