This is an interesting political question. Most people will probably agree that states are indeed justified creations. A lot of people will disagree on the origin and means by which they were justifiably created, however, and this in turn results in the discussion of what are the justified powers of a state and how might the state accrue them. 

So my question is: how do states form, who is able to form them, and why do they represent the opinion of all individuals residing in a land, not only at the time of creation, but for generations afterwards? 

An example of an answer to these questions would be: I believe that states are formed by an implicit social contract derived from human nature in societies. When one is born in a land with positive and negative externalities induced by the efforts and achievements of others, in order to stay in this land, one must accept this implicit contract ........... (so on and so on)

If you don't believe the existence of the state is justified, possibly describe your concept of which spontaneous order would be the likely product if the state were not to exist. 

Individualism only functions within a state context. Libertarians should not argue against the Existence of the state as a whole (while we can accept arguments about the scope or role of the state), but in any sort of situation where some unit of humans larger than a single household is interacting, a state is needed to protect individual rights. A contract of mutual property respect could exist between households, but who enforces that contract? How do we make sure these enforcers have an optimum level of accountability to make sure that they are enforcing contracts in a consistent and unbiased manner? Thus we get to the idea of the state, and a structure of legal enforcement.

The most reductionist view of the state is a neutral party with unlimited ability to enforce (voluntary) contracts between individuals or organizations. Now i have often seen libertarians argue that the social contract which we are born into is involuntarily, and that especially giving individuals a lack of "Exit" choice is what makes the system tantamount to slavery, and therein a more valid debate could be held, but in the realm of purely private matters, the state must exist to give some sort of force to a person making a contract, to give someone incentive to stay true to their word.

This threat should not have to come from the other party. In signing a contract with my employer, they should not be afraid that I will go knocking at their door with a shotgun in hand because they fired me in a manner which was in breach of contract. They should not fear my ability to enforce the contract by force, arbitrarily as an individual. They can fear a lawsuit, but that's a much less existential fear than a "street justice" form of contract enforcement. Similarly, we can't just let the market "deal" with contract-breakers by having nobody choose to do business with them, because this creates an environment where a lot of dead weight is created due to fears of entering an unenforceable contract. Individualism cannot function without contract law, contract law cannot function without enforcement, and for consistent, unbiased enforcement, you need a fixed state to provide a common framework for parties to operate in.

The thing of it is that we cannot guarantee our freedom to be individuals without the state. Therefore if you value individual liberty, you must acknowledge the need to create a state

(note that my views are couched in a kind of marxian utilitarianism, not classical liberalism, so you see some of why i truly believe we need states in my argument here, but these are not my views, instead a polemic stating why right-anarchists should not argue for the dissolution of the state)

 I think the issue is how a minarchist (or statist in general) views contracts vs. individualist anarchists. There is a good article on the matter found on mises.org. The author compares the Rothbardian (or anarchist) subjective value theory with Randian (or minarchist) objective ethics and how contracts would be enforced according to the two different philosophies. The basis of their enforcement differs because their definiton of what a contract is differs. Rothbard views a contract as a claim of a future action, while Rand views it as a legally bound obligation. Anarchists don't believe the fixed state is unbiased and consistent, and believe competing law enforcement would be more efficient at dealing with criminals. It is a very complex legal system (as is a statist one) but it is certainly just as logically contained. 

http://mises.org/daily/4698

I make a contract with you to exchange my dog for your hen. I gave you my dog. You now say, "Sorry, I refuse to give you my hen. I love it too much."

Clearly, you are morally in the wrong, and a just system of laws would imply just that, when applied to this case. But why are you in the wrong, what are your liabilities, and what is the way to right the wrong? Here Rand and Rothbard would differ. Since neither of them has ever considered in writing this specific example, I allow myself to represent their positions as I understand them.

To begin with, Rand would say that you are wrong because you have defaulted on a promise contained in a contract. You owe me a hen, because you have promised to give me one once you possessed my dog. Your debt has been incurred by your promise. This is a matter for a civil court, dealing with restoration of justice damaged by contract violation.

Rothbard, however, would say that you are in the wrong for a different reason. You don't owe me a hen. The hen is yours, and remained yours. As for the contract, your default amounts to a cancellation of it. The contract ceases to be valid once one of us refuses to abide by it.

But if so, what makes you morally wrong? Simply the fact that you now control a dog that belongs to me makes you a criminal. Once you have, by refusing to fulfill your part of the contract, cancelled the contract, you have thereby cancelled your right to control the dog. If you continue to hold the dog, you are in the same category as a robber, or a thief. You control and use property that belongs to another without his permission, by force. Thus, the correct procedure to right the wrong is for me to sue you at a criminal court.

Observe the difference: For a Randist, a promise creates an obligation. You are free to make a promise. Once you have made it, you are not free, morally speaking, to default on it. A later decision cannot cancel the prior decision. Once you have promised to give your hen, when certain conditions have been satisfied, the satisfaction of these conditions transfers automatically the hen to me, from the point of view of the right to own it. If you refuse to deliver the hen, you are trying to detain the transfer of property that is already not yours. But the dog does belong to you.

For a Rothbardian, though, a promise does not create an obligation. A promise is a declaration of an intended action, or a declaration of a present decision to do something in the future. It has no moral significance beyond that. The same fundamental freedom of choice that makes it possible for you to promise makes it possible for you, later, to cancel the promise. You cannot be sued for canceling promises.

This is a large difference, and it relates directly to the opposing views concerning minimal government. For Rand, the contract that makes individual rights defensible is a contract with a government. Hence, for her, libertarianism is impossible without a government: it presupposes a government, albeit a minimal government.

For Rothbard, individual rights are independent of any contract, they are natural, and the fundamental defense of them is by the individual himself. The marketing of defense services through defense agencies is not in any way a necessary ingredient in the implementation of rights. Rather, it is a special case of the principle of specialization of services on the market, and has nothing to do with the moral validity of individual rights, nor with their implementability.

I would disagree with the latter point. There is no hypothetical scenario where individual rights are defensible without (the bad kind of) anarchy ensuing without a state entity to enforce the most basic laws. A million individual biases play out in a million interpretations of reality, and the myriad lawsuits in the courts today demonstrate how easy even a simple contract can be deemed in "breach." What if you got a scrawnier hen than you expected, and decided ex post facto that it wasn't worth the dog you gave? You assumed a certain degree of utility when getting the chicken. Now what if you can credibly claim the seller was deceiving you on that point? Or at least try to do so?

The courts and the individuals who enforce the will of the courts need to be a larger entity in order for the system to function with any consistency.

I have to disagree. The existence of common law refutes this. It is an example of spontaneous order without the legislative processes of a state. 

http://en.wikipedia.org/wiki/Common_law

is law developed by judges through decisions of courts and similar tribunals, as opposed to statutes adopted through the legislative process or regulations issued by the executive branch.

In an anarchic society you'd have multiple competing courts forming decisions chosen based on their ability to obtain the justice one seeks. The court would likely appeal to aspects of natural law to form its decisions, but it is not precluded to that (you can have socialist courts that don't believe in property rights, but nobody would deal with them if socialism is unpopular.) As for your scenario where you get the scrawnier hen, the burden was on you to find the information you needed to obtian what you wanted. Now if the other party promised a hen that wasn't scrawny, and doesn't deliver it, it is the same as him/her not paying you the agreed upon price of a product, and is consequently theft. You can then take him/her to criminal court for stealing your dog. 

Another example of anarchic law is that found in medeval Iceland. 

http://mises.org/daily/1121

Instead of a judicial branch of government there were private courts that were the responsibility of the godar. To solve disputes, members of this court system were chosen after the crime happened. The defendant and plaintiff each had the right to pick half the arbitrators. There was another level of courts called the Varthing. This was a Thing court in which the judges were chosen by the godar of the Thing. Then there was the National Assembly or the Althing. Each quarter was represented by their own Althing. If a dispute was not settled by the private courts, the dispute would go up the ladder to the next highest court until the dispute was resolved.

There was no public property during the era of the Vikings in Iceland, all property was privately owned. 

The settlers of Iceland divided the country into 4 regions. Each region had 9 godord and the godord were divided into three things. The godord were divided into groups of three and each thing had three godord. 

The word 'godord' has two definitions. Godord represented a group of men. These men gave allegiance or alliance to a specific godi. A godi is the leader or chief who constructed a place of worship for his pagan followers. The godord was also a collection of rights, the right to represent the law making body of Iceland.

David Friedman states, "…seats in the law-making body were quite literally for sale."  These men who were law-makers did not have power just because they held the title godord. They were powerless "unless he could convince some free-farmers to follow him." This kept tyranny and injustice in check. 

David Friedman, a consequentualist Anarcho-Capitalist and economist, has written many books on how Anarchic law could for through spontaneous order. 

http://www.daviddfriedman.com/Academic/Anarchy_and_Eff_Law/Anarchy_and_Eff_Law.html

https://www.youtube.com/watch?v=yXWFWIM8OCI

You keep beating around the bush that is enforcement. The godordi here gained power to enforce through consent of the governed, because they had followers who could then enact the court's will, ensuring that laws had meaning and therefore that the society could function and these property rights could be respected. This is a state setup, what you're describing. Something resembling a direct democracy, but a state setup.

That Rothbard sounds like an asshole.
A contract doesn't mean anything? That's really destructive.

All it does is penalize the wrong-doer, without remunerating the other. Sure a thief can be taken to court and put in jail for stealing your car, but who is going to pay the victim for all the car rentals, missed appointments, and general stress of the matter? And what if the thief runs a car stealing business and simply has stand-ins take his place at trial? It seems to me that people who abide by contracts are really the ones who suffer here.

I can't even imagine how fucked trade would become, with corporations needing parts from thousands of sources. A rival could simply pay another company to stop providing an integral part, and then all hell would break loose....and all they would be charged for would be the parts "they stole". That's a fucking frightening scenario.

I think the term "social contract"is one of the biggest lies in humanity to justify the creation of a state. Some people take state and society as the same but the first implies force and vinculation even if they dont have your consent.

I think that if you justify the existence of a state with liberty, you cannot do it basing the argumentation in a "contract" in which there isnt any will to sign in the first place, a forced contract

So no, I do not think there should be states, I would prefer private(meaning small communities or anything that isnt related to the state) association. I dont know if it would be convenient, but at least I think it wouldnt be wrong

Edit: My first language is spanish, so most of the words I used may not be the same in english. Just for you to take in consideration

States right now are an arbitrary thing to begin with. Not everyone agrees what defines one as a state. This is a question that has multiple parts to it because it also brings up "justification" which is a question for philosophers, but defining states is something for politicians.

I am taught that for one to be considered a state, you need to have sovereignty over a piece of territory, have a monopoly on force (violence), and I believe the last one was that other states have to recognize these things and consider them to be a state as well.

I would rather not answer the question because it's not really an intellectual one and more of one about your own personal morals and biases.

There was a government (not a state), but it wasn't responsible for the enforcement of laws, that was entirely the choice of the individual who recieved damage. They could seek reparations personally, or they could have the godord or some other representative buy that right.  That is by definition not a state, because the use of force is not monopolized and contained in a geographical region. The judicial system was entirely privatized. You chose which legal system you wished to abide by, the other party chose his. The godor resolved the issue. A state would not allow you to buy a legal system, there is only one system depending on where you live and it is the state's sytem (contained within a geographical region <=> state.) 

Iceland did not have an executive branch of government. Instead of a king they had local chieftains. One permanent official in their system was the "logsogumadr" or law-speaker. His duties included the memorization of laws, the provision of advice on legislative issues, and the recitation of all legislative acts one time while in office.

Jesse Byock states in his book that, "leadership evolved in such a way that a chieftain's power and the resources available to him were not derived from an exploitable realm." This was because free farmers could change allegiance between godi without moving to a new geographical location. "The legal godi-thingman bond was created by a voluntary public contract."   The ability to switch legal systems with out moving, is key to a decentralized system. It creates secession down the level of the individual, making all governance structures formed truly voluntary.

How were people held accountable if they did commit a crime?  In much the same way as the current United States civil court system works today. Criminals were forced to pay fines. These fines did not go to the state, but were restitution. If the criminal could not pay the fine imposed on him, then he could go to his godord or a group of family and friends, or some other alliance, and have them pay the fine for him, or if no one would represent him, he could work the fine off via slavery. The poor were at no disadvantage. The poor could sell their right to justice to someone, such as a chieftain or another respected peer, who could collect or make right upon the victim. In this respect, the right to transfer restitution acted as an equalizer for the poor. In cases where the victim did not want restitution, the guilty parties had no obligations imposed on them.

If a criminal would not pay his fine or submit to slavery, he was either outlawed or would possibly lose the support of his peers, depending on the severity of the crime, eventually discrediting himself.