Is Vigilantism justified when the government fails to enforce the law?
QUOTE:
"By first glance I actually want to take two positions on this (which is good for debate cause you have to take both sides)
For justice i beleive that we cannot involve in vigilantism because you are not giving suspect a trial. And since the suspect is innocent until proven guilty, you are punishing an absolutely innocent person which is not achieving justice in anyway."
In France, suspects are guilty until proven innocent? Does that mean vigilantism is justified there? I believe you're confusing someone "actually being innocent" and someone being "presumed to be innocent". The law presumes people to be innocent until proven guilty, it doesn't state that they are actually innocent. It's a minor distinction, but an important one. Besides, I believe the issue of vigilantism goes beyond whether the law presumes you to be innocent or guilty.
You may want to examine the reasons humans developed courts and the consequences of allowing any citizen to carry out their own brand of justice against perceived law breakers. I mean...there's a reason vigilantism hasn't been allowed in England for ages and I assure you....it wasn't because of an overwhelming concern for people's human rights 
Also, I was reading a brochure from my home town the other day. My hometown plows all city streets within 24 hours of what they call "snow events". To accomplish this, council passed a by-law prohibiting people from parking on the streets until 24 hours after a snow event (or presumably, until their street has been plowed). If you fail to comply, you will either be ticketed $80, or (if they need to move your car to plow) your car will be towed to a nearby location at your expense.
So what's the point? The point is, that on this brochure, my city included a warning: "Cars will not be towed or ticketed based on information from the public". This prevents my neighbour across the street, whose sole pleasure in life comes from tormenting me, from calling 5 minutes after a snow event and getting me ticketed. Think about it.
Law enforcement officers and the courts are fairly unbiased organizations. Are people? Is it possible that people are more likely than courts or policemen to be swayed by personal dislikes, friendships, self-interest, racism, homophobia, a hatred of young people, neighbourhood feuds etc.? Can you trust the observations of someone who is biased or invested in a certain outcome?
The courts will punish a black person who is caught vandalising a school. The courts will punish a white person who is caught vandalising a school. Your neighbour is a vigilante. He punishes the black people he sees vandalising the school, but not the white people. Is that justice?
Your neighbour hates you. He scrutinizes everything you do, researches archaic laws that were never repealed, and punishes you for every violation. He ignores everyone else, even when they blatantly violate the law. Is that justice?
What is the purpose of the law? Is that purpose served by vigilantes who selectively enforce it based on their own personal predilections? Is that justice?
How do vigilantes decide what level of punishment is appropriate if they're punishing the perpetrators?
What are the reasons for punishment under the law (e.g. In many tort cases, the purpose of the damages is monetary restitution)? Are those purposes served by vigilantes who punish people based on their own personal predilections? Is that justice?
C and D commit the exact same theft in the exact same way. Vigilante A gives C 10 lashes for stealing. Vigilante B cuts off both of D's hands. Has D been unfairly punished? Has C not been punished enough? Has justice been served in both cases? Courts have limits on what they can do to people. They also have guidelines for sentencing for serious cases and a stack of precendent much of the time that they use for guidance. Vigilantes can do anything they have the means to do. Is anything they do considered justified? How do you limit what they do?
If I defame you, and you decide to carry out an act of vigilante justice...what do you do? How do you punish something abstract like damage to your repuation?
Are a single individual's arbitrary decisions justice?
(Another useful question to think about is why common law countries began to use a system of precedent and moved away from the arbitrary decisions of judges)
Then you have problems with escalation.
I commit a theft.
Because I committed a theft, you punish me by cutting off my hand.
You cut off my hand. That's a battery (an assault in criminal law).
Because you committed a battery(assault), I cut off your hand and add in your foot to deter you from future crimes. Those actions are also batteries.
You approach me with a knife to punish me for my batteries.
Fearing for my life, I kill you in self-defence.
Who's right? The thief committed a crime. But technically the vigilante committed a crime when he chopped off the person's hand. He had no right to do so under law, and was in fact, prohibited by law. So the person with the missing hand has a genuine grievance against the vigilante. So where does this stop? Who steps in a finally says that that's enough? Who has that authority and the power to do so?
(Escalating feuds were a contributing factor in the development of the common law in England)
QUOTE:
"But morally, vigilantism is justified because if you see a fellow citizen being murdered, then you have a moral obligation to help out your fellow citizen. Although, under law the person you saw shoot the gun at your fellow citizen is innocent, you have more common sense than that and can arrest that person atleast until law enforcement starts to work again. And also according to the social contract, you have no duty to uphold your side of the contract if the government doesn't hold up it's side of the contract. The governments only obligations are to protect your rights to life, liberty, and property. So under the social contract it is totally justified."
Your first argument doesn't work. I'm not sure which country you're from, but in many countries, under the law, citizens have the right under law to make what's commonly called a "citizen's arrest". In doing so, they may arrest someone whom they see committing a crime (generally they have to see it, not suspect it...police can arrest based on suspicion however). They are then under a duty to treat them humanely and turn them over to the authorities as soon as possible. That's not really vigilantism. I mean, you could try to argue it is...but it's a weak argument.
Your argument about the social contract may be hypocritical. On one hand you're saying the government has failed to uphold its side of the contract, and thus you no longer have to uphold yours and can ignore their laws. On the other hand, you're saying that the government's laws still apply, and are valid reasons for carrying out your brand of justice.
Unless you're creating your own laws....which raises a whole host of concerns.
P.S. What kind of laws are we talking about here? For instance, many laws aren't meant to be enforced all the time (e.g. parking by-laws). Parking by-laws for instance are only meant to be enforced occasionally. The city's goal isn't to nab every illegal parker out there. That's impossible. Just to nab enough of them that it deters people from parking illegally. Obviously, for murder, the government wants to catch and punish every murderer.
The uncertain parameters of the question make it difficult to be of much help. I'm not sure if you're talking about a parking ticket situation or a situation where a government that is close to collapse, chaos is reigning in the streets, and the government is unable to enforce any laws.
To serve is to survive