Well, not to get too far off topic, but the Justice League has similar standing with its government(s) as S31. No authorization for its existence, no chain of command related to government authority, and no responsibility to the populace or the government. But they're "good guys" and S31 isn't? Is it the lack of government-backed legitimacy that is bad, or is it the actions taken that are bad?
Batman's a vigilante like Sloan. What's the real difference between them? Their actions.
the "justification" used for Batman's vigilantism is that he has his rule of "no killing," or else Commissioner Gordon and others would view him more like the Punisher, I guess. (leaving aside the absurdity of a Human vigilante who doesn't use guns and fights criminals who DO, somehow always being able to defeat his opponents without ever killing them, even accidentally.)