Halacha punishes theft with a financial penalty. Rav Moshe in Orach Chaim 5-9,11 and Choshen Mishpat 1-8 says you can’t support or have a Jew punished by the secular authorities because they administer a punishment in excess of halacha.
Once again, I’ll discuss the issue of what punishment, as well as Bais din vs. Government on another thread. Also, not sure where “support or administer” comes in to the Halachos of Moser or Shevuas Shav (which the second certainly wouldn’t apply in an American court, and the first is if the Nignav is yourself, not the government). Also, this is Ei Efshar B’acher, and Rav Moshe agrees that then it is Muttar.
Suddenly haskem vehargo is not a halacha?
Sending someone to jail is not haskem vehargo. We can discuss the parameters of Rodef, as well as current applicability to a non-active murderer (if he was one, which you don’t have two eidim), on a different thread. Otherwise I’m not sure what you are trying to get at.
My point was that in certain situations, the government (who has the chyiuv to make rules on its own land, and you agree to abide by them by living on the land) can jail someone, even if pure Halacha as stated in the Torah would not say that person should be jailed. If you want to argue that the appropriate punishment should be something else, that is for the thread that EretzHaK is going to start. When you do, I will bring in the Rambam in Rotzeach 2:4 as a source for what to do with Levi Aron.