From San Diego Lawyer Peter M. Liss’s blog:
Over the past decade, more and more people have taken to the streets in body armor, striving to become real life superheroes. While any wannabe heroes may not be able to develop powers, like Wolverine or Spider-Man, anyone who is brave enough can choose to fight criminals the way Iron Man and Batman do. But is this form of civilian justice legal in America’s finest city? San Diego criminal lawyer Peter M. Liss says “yes,” but only up to a point.
The basic legality of being a superhero in San Diego comes down to how the hero goes about stopping crimes. Citizens arrests are legal in San Diego, but the person stopping the crime is only permitted to use the minimal amount of force necessary. That means you couldn’t run around murdering, torturing, kidnapping criminals like The Punisher and then tell your San Diego criminal attorney to explain to the police that it’s ok because you brought to justice so many people to justice.
If you behaved like most superheroes from the Golden Age of comics and merely subdued the criminals enough to bring them to the police station, you’d be acting within the law. This doesn’t mean you couldn’t use weapons, even a gun, it just means that you could only use them when appropriate -for example, if the criminal started shooting at you. At that point, even if you were arrested for your actions, your San Diego criminal defense lawyer would be able to explain that you were attempting to perform a citizen’s arrest and then had to use a weapon in self defense.