This really isn't a mechanic for your game but more so a flavor to add to your game, to basically put some realism or fear into the players of their character that being a masked Vigilante is against the law. You don't have to use this, but if you do, it will make the player's job even harder as they will have to be more creative with their character choices and be more sneaky in their crime fighting duties. Maybe they will think twice about going out to fight crime, when the police force is ordered to capture Vigilantes and bring them in. While I do a lot of street fighting level games, I will normally implement this law after a certain amount of time when the players get really comfortable with just out right doing things with their characters. While the people may respect the man behind the mask, and sometimes the law will as well, vigilante activity should be done in secret and from the shadows.
This also did happen on the show, when Oliver Queen because Mayor of Star City, but he put the vote to the people of Star City, and the measure passed by a landslide. While I could find no actual wording, or things defined based on the show, other then the name "Anti-Vigilante Legislation". I even made up the legislation number docket to make it seem more "official". Enjoy!
Anti-Vigilante Legislation (AVL 9A.16.020)
Any person caught fighting criminal activity within the limits of the city, taking "crime fighting" into their own hands, by using physical force to stop criminal activity that is above and beyond protecting themselves from immediate danger or protecting personal property will be considered obstructing justice and acting in an authoritative capacity which is not authorized by the city. Elected & Appointed officials are to arrest and detain Vigilante activity by any means necessary to uphold the laws of the city.
AVL 9A.16.020 allows use of force in these instances:
• When used to arrest someone who has committed a felony and deliver the suspect to a public officer.
• When used by a party about to be injured or about to suffer "malicious interference " to his own property. The force must be "not more than is necessary."
• When force is "reasonably" used by the owner of property to detain someone who unlawfully enters his property.
Vigilante Defined
A vigilante, also known as a "mask", is an individual who takes the law into their own hands, believing that the police and the court system are unable to or unreliable at bringing criminals to justice. However, not all vigilantes are fighting for justice, some do it out of personal revenge or antagonistic reasoning. It is also common for vigilantes to take on a moniker to be known by, some by personal choice and others by having been named by the public. Some vigilantes eventually gain a level of popularity and admiration from the general public that they begin to be seen as a "superhero". Despite the name suggesting this term is reserved for individuals with superhuman powers and abilities, it is also used to define individuals without any but instead rely on combat skills, intellect, or gadgetry.
Vigilante Justice
"Vigilante justice" is often rationalized by the concept that proper legal forms of criminal punishment are either nonexistent, insufficient, or inefficient. Vigilantes normally see the government as ineffective in enforcing the law; such individuals often claim to justify their actions as a fulfillment of the wishes of the community. Persons alleged to be escaping the law or above the law are sometimes the victims of vigilantism. Vigilante conduct involves varying degrees of violence. Vigilantes could assault targets verbally and/or physically, damage and/or vandalize property, or even murder individuals.