What makes a person a criminal? The simple answer is, the law determines for us who stays free, who pays a fine, who goes to jail and worse. But while it's easy for the law to see things in clear black and white, in the realm of human interaction, things get horrendously fudgy.
Laws change retroactively, in response to disastrous events the repeat of which we hope the new laws will protect us from. But what if by enacting new laws, a group of people who were once tolerated by society suddenly become lawbreakers simply because the new laws say they are? Or what if the beliefs of a group of people suddenly become outlawed overnight and they have to decide to abandon their beliefs or face legal consequences?
In the light of religious extremism and senseless terrorist attacks on secular society, society usually seeks the protection of the law to preserve a sense of security for daily existence. In the US, for example, new anti-terrorist measures have been enacted by their lawmakers; but such measures have also caused concern that the citizens' civil rights and liberties have been sacrificed as a result.
Marvel Comic's recent "Civil War" story arc is a modern day parable for the fear and tension against the unpredictability of life and death as we recognize that terror strikes anyone, anywhere, anytime. No one is safe, no one is innocent, everyone is a target.
It isn't an act of terrorism that sparks off the Civil War. It is an irresponsible act of nationally televised super-grandstanding by a group of inexperienced costumed heroes causing a horrific disaster in Stamford, a peaceful residential suburb. The death toll runs in the hundreds, the majority being children from a neighbourhood school, the calamity's ground-zero.
Thus, the move to press a Super-human Registration Act into existence. This Act by law eradicates any protection superhumans have of their secret identities. The law compels all superhumans to be properly trained and carry a Federally approved licence, their activities having to be officially sanctioned by the US government. In other words, they have to become civil servants if they wish to continue righting wrongs, doing justice and preserving the American way. By implication, it will also become the government's decision as to who registered superheroes go after.
The new law, such as it is, splits the superhero community asunder: those who feel that registration is the right and responsible approach (notably Iron Man and surprisingly, Spider-Man, and those who never had a secret identity in the first place, like the Fantastic Four), and those who feel that secret identities have to be protected (for fear of reprisal agaist their families and loved ones, or just at least having a chance to lead a normal life on the side) and that what they do should not be government-controlled or directed (biggest surprise for this faction is Captain America -- chief protector of American values or something like that).
In one early incident that causes the superhuman community to have a very serious think over this situation, the Fantastic Four's Human Torch gets hospitalized by a very angry, very human mob who recognizes him (he is a public figure, after all) and attacks him outside a nightclub while he is there on a date.
Because a new law is called into existence, many superheroes who refuse to abide by it become super-villains overnight, and are being hunted down by others who were once their friends and colleagues. Some previous super-villains who choose to abide by the new law suddenly become elevated to hero status as well, so the whole Marvel Universe is in massive turmoil as loyalties change, battle-lines are drawn, and casualties mount.
What makes a person a criminal? The Law. Whose side are you on?