Just so you know, the Supremen Court reversed the 9th Circuit in this case and left the FTCA as the only remedy.
I don't care, it was just an interesting but macabre diversion.
It turns out that the subject of this thread is bogus, just another urban legend bouncing around the internet:
Both cases were entitled "Castaneda v. USA", but the one relevant to this thread apparently was dismissed by the district ct. in 1997 with no such precendent establish (district courts decisions don't establish precedent anyway), and the sheriff made no such wild claims.
Which explains why Google search didn't turn up anything on legal sites relevant to the Wyoming story ....