There can be perfect human beings but there can never be perfect systems.

This is something I've repeatedly said and I've been called both dark and hopeful at different occasions. The truth is that I'm both. My experience is that people always tend to underestimate both the good and the bad of human kind. Never underestimate the extent of the skies or depth of the abyss.

Our future lies in the goodness that is devoid of hate, greed and ignorance. But in the path to better ourselves we should know the extent of evil. The virtue of the one who is well versed in evil is great and such people are not just incorruptible by evil, they also know to defend themselves.

These days there are lots of talk about politics and laws. There are also lots of political movements about humanitarian causes and making people do the good things. But most these laws and political movements are nothing but a farce because of one fundamental reason: You cannot legislate virtue into existence. You cannot make sins disappear by making laws. Only the uninformed, retarded and the malicious would say that the laws can bring forth the good or get rid of evil.

If making something impossible makes someone good, then in all goodness go worship a tree as it has probably not hurt a single man, woman or child and I'm sure that tree had never done crystal meth or something. Go make a temple for your kitchen sink as it has done no bad thing in its entire existence. Human actions are governed by the human mind. One's own individuality is the final frontier in absolute terms. The only way you can truly control a person is by taking over someone's mind effectively erasing his/her existence. That shouldn't be the point of law.

Then what is the purpose of law and what is Justice?

Human actions cannot and shouldn't be controlled. Incentives can and should be controlled.

Additional Reading: https://mises.org/library/human-action-0
The law shouldn't exist to tell people what to do but to tell people what shouldn't be done. There is only one thing that is universally unacceptable in a society that is not due for self-destruction. That is aggression. If a society wants to prosper and to live in freedom, it is the Non-Aggression Principle that should be enforced. So what is this NAP?

A commonly used illustration of the NAP (AKA Law) is that a person has a right to swing a stick in any way he/she likes as long as it stops before the other person's nose. There shouldn't be laws telling people how to swing a stick and as long as nobody is hurt, law or law enforcement has no business to attend to. Every individual has the right to life, liberty and pursuit of happiness. This statement is sacrosanct. There can be no compromise on a person's life, liberty and pursuit of happiness under any circumstance. Any freedom that infringe on another's freedoms (An aggression) cannot be tolerated. This is the Non-Aggression Principle and there can be no compromise.

The purpose of law is to ensure each individual's sacrosanct right to be not aggressed upon.

• Aggression is wrong.
• Might doesn't make anything right.
• Anything that doesn't violate NAP isn't wrong and shouldn't be acted against.
• Force can only be countered with equal or greater force.
• Anybody has the right to agrees against the first breach of NAP as long as the following aggressions doesn't far exceed the original aggression.
• Right permits might.
• Acting against a first breach of NAP isn't a crime although it could be morally impure/ a sin.

“Life, liberty, and property do not exist because men have made laws. On the contrary, it was the fact that life, liberty, and property existed beforehand that caused men to make laws in the first place.”
― Frédéric Bastiat, The Law

The last 2 bullet points are very important. Unless the whole system of law and justice would be a Catch-22 logical paradox. To clarify this we need to look at why we need law and justice in the first place. Those 2 things do not exist to get rid of the evils of the world or to promote good. Virtues and sins are not like fiat that can be brought into existence by decree. Human actions can only be influenced. There will be people who'd do good no matter what and there will be people who'd do bad no matter what. Most would be somewhere in the middle. Basically it's like an internet forum.

If we need to keep this Law and Justice around, then it must serve some function and add something to the society. Else it would worth nothing more than some custom. Law and Justice should somehow supercharge the well being and prosperity of human civilization. Aggression hurts individuals and what's bad for the trees is bad for the forest.

Law and justice is an incentive structure

It's purpose isn't to do good or stop bad things from happening. The utility of law is screwing on aggressors and making the lives easier for those who do not violate the NAP. Since only force is the only thing that can counter force, violence is a primary part of violence prevention. This is where the 2nd aggression comes into play. Justice is more or less pointless after the damage has been done. Prevention is better than the cure. The greatest justice is the prevention of crime. A crime is an aggression against a person's life, liberty, property (which would obstruct his/her pursuit of happiness). Law & Order should under no circumstance should punish the second aggressor for anything that doesn't go above neutralizing a threat to a non-aggressor's life, liberty, property.Justice is pointless if it's a stable that is closed after the horse has escaped. The point of Justice is allowing framework for the Non-Aggressors to become immune to aggression.

How to become immune to aggression and the path of least resistance

People make choices and there will be those who stand by their principles. But they don't matter in a discussion about law and justice. If people don't hurt other people, there won't be any need for justice. The problem is the people that would hurt another when given a choice. For these guys, we must make choosing the good path easier and the aggressive path more difficult.

My question is what if anybody who pull out a weapon to kill another person is allowed to be killed by anybody and no second aggressors will face any legal consequences, how would potential killers would act?

There will always be kamikaze types who'd do bad things no matter how difficult just as there are people who'd do the right thing no matter what. Law has no effect on those minorities. But when it's open season against violence as long as the second aggression does not far exceed the first aggression, we have an incentive structure that efficiently minimize violence in a decentralized way. Such a system would even allow more aggressive personality types to positively contribute to the prosperity and well being of the society.

In a system like this Batman would be considered merely a market phenomenon like https://quantstamp.com or white hat hacking where an individual use violence in a socially constructive manner and the only question people would be asking is: Who shot first? If Gotham was like this, most villains would be killed by random civilians and Batman would be without a cause to fight for and may end up having to take out his angst on..... I don't know........... consensual BDSM or something.

The separation of Law and Morality

Just as economy and religion needs to be separated from the state, the morality must be separate from law as law has absolute zero effect on human morality. Only the individual can engineer their mind to a higher spiritual level and only through wisdom can one achieve such spiritual development. A man can take 500 horses to a lake. But not even an entire army is capable of making one horse swallow the water. As a Buddhist I consider hurting other as something that shouldn't be done. But I am against punishing people of 1st degree murder who were at the clear and present risk of getting killed. If a group of armed personal break into one's property the owner should not be punished for killing them before they do any killing of their own. Punishing such acts is a slippery slope into a Gandhi-esque protest against violence where its open season for all aggressors.

“You say: "There are persons who lack education" and you turn to the law. But the law is not, in itself, a torch of learning which shines its light abroad. The law extends over a society where some persons have knowledge and others do not; where some citizens need to learn, and others can teach. In this matter of education, the law has only two alternatives: It can permit this transaction of teaching-and-learning to operate freely and without the use of force, or it can force human wills in this matter by taking from some of them enough to pay the teachers who are appointed by government to instruct others, without charge. But in the second case, the law commits legal plunder by violating liberty and property.”
― Frédéric Bastiat, The Law

Some people would make a choice to die and get raped than lift a finger against someone. But that is a personal choice. Law has no place in a person's spirit. If you let laws decide morality (which is a technical impossibility) you'll loose both the safety in this world and the guidance to another. Do not confuse morals with laws. It worked well with alcohol prohibition.If the violence that act as a deterrent against violence were to be punished, we'd only be left with a mound of dead people that were good and a few of bad people after they've done all the damage.

“Legal plunder has two roots: One of them, as I have said before, is in human greed; the other is in false philanthropy.”
― Frédéric Bastiat, The Law

When given a choice, many would pick the easy path. There is no reason any peaceful individual should fear a government or a criminal. First there was life and that life was free. Governments came later and so did assholes. No authority or criminal has the right to tell you sod off and die instead of defending your life and liberty. The Evil prosper when the Good people do nothing; Don't castrate their ability to do something.