“Cases of Rebellion or Invasion the public Safety may require it”
Except the 2012 NDAA doesn’t require invasion or rebellion. It simply requires the federal government to deem a person a target.
I don't remember where I saw it, but there was a conspiracy-theory type article I was reading which essentially claimed that some act (War Powers Act?) labeled the inhabitants of the US as enemies (argument that the civil war let the federal gov't conquer the States, thereby depriving the state-citizen of any rights)... if that is at all true, then We The People are the invasion, and asserting your rights (or state rights) is rebellion.