After all, our German Nazi-regime was ruling (and killing) (mostly) perfectly within its own laws.
Later on, after we lost the war, some people actually got the rope for their crimes (admittedly, only those who didn't run fast enough, weren't killed already, couldn't blame someone else or didn't have anything to bargain with (like a prospect of owning nuke-bearing ICBMs or a list of Soviet spies)).
So, if a future government, supported by enough people, wanted to override this exemption, I don't see that not happening. In theory.
Granted, it will be difficult to override, but as we know: the easy things are the most difficult