It bothers me that I haven’t come up with a better name than Superhero World as of yet. Maybe a fictional comic book company though I really imagine the setting as more of a TV Supers setting.
Assuming that the players are going to band together, they’re either going to be with the law or against it. Knowing players everywhere they’re going to be with the law except when it is inconvenient.
This is where U.N.S.A.I.D. (The United Nations Security And Intelligence Division) comes in. They are nominally in place as a means to combat evil and terrorism across the globe. Depending on the PCs actions, they need to watch out that they aren’t labled as both.
Even if played as a completely white hat agency, they are still a great souch of PC backgrounds and Rogue agents intent on destorying the world. More than likely though they will always consider the PCs a threat and have agents in place to manipulate or neutralize them if things go wrong.
The point is, even heroes have authority to deal with.