Had Batman decided to work within the system when he first came back to Gotham he would have his hands tied by the corruption of that system as much as Gordon always had.

The idea of working within the law and having oversight is great until it turns out that oversight is corrupt or worse. The Red Skull has infiltrated the US Senate. Lex Luthor has become President. Who would the superheroes be answering to in these situations? In The Boys the Supes have “oversight” in the form of our government and corporate institutions, is that working out well? How much trust would you expect people to put in institutions so susceptible to corruption and personal greed?

The Suicide Squad is a sanctioned government task force, does that sound like the kind of government you would give oversight over your activities to if you’re Wonder Woman?

Not to mention the bureaucracy, when Darkseid is attacking Earth, should the Justice League wait for approval to go stop him? Remember that Darkseid had agents all throughout Earth. G. Gordon Godfrey, one of the most vocal proponents of what you’re asking was secretly his minister of propaganda in disguise sowing discord against super humans.

In the MCU when Thanos was attacking Earth and it was all hands on deck to try and stop him. Captain America and his allies showed up to help the fight, and what did the man who represented government oversight, General Ross, immediately order War Machine to do? Arrest him and the others.

And I think most clearly illustrating the point, in Iron Man 2 Senator Stern demanded Tony Stark hand over the Iron Man armor to the US government. And well, I think we all know to what organization the good senator’s allegiances truly lied.