I always figure that the actual 'arrests' that superheroes perform are mostly non-starters in court, but at the same time the heroes are not interested in filling up the prisons: they want people to stop committing crimes. If they stop knocking over stores because they're afraid of going to jail, or because they never know when some costumed kid is going to fall out of the night and beat the crap out of them, it's all the same to the heroes.