If there is a characteristic which unites all human societies, past or present, it is surely an inordinate fondness for violence. Those who can force others to submit to their demands will do so until they meet a greater force.

We tend, in the superficially peaceful communities of the rich world, to forget that violence is the underlying determinant of human relations, and that this violence, far from disappearing, has simply been distilled into a political system which both protects and threatens us. Though we may avert our eyes, our respect for the law rests upon our recognition of the state’s capacity to compel us to submit by force of arms.

This, though it arose from centuries of arbitrary power, is the social contract upon which those of us who live in nations with elected governments appear to have settled. The state claims to protect us from external aggression and the violence of the powerful, and in return we surrender to it (unless we live in America) our weapons and our own capacity for violence.

The paradox of governance is that a state which is sufficiently powerful to protect the weak against the strong is also sufficiently powerful to crush the weak. History suggests that it will do so whenever its citizens fail to hold it to account. Indeed, the ultimate restraint upon the violence of the state is the violence of its citizens, who might seek to overthrow it if it abuses its powers. The great innovation introduced by democracy is that it permits us to remove the monopolists of violence by non-violent means. The great problem with democracy is that it permits us to replace them only with another set of monopolists.

Viewed in this light, our political systems appear deeply unattractive. But, as the people of Somalia and the Congo (or, for that matter, the victims of America’s lax gun laws) are aware, the alternative appears to be even uglier. Without protection, the weak are trampled by the strong.

So our social contract, repulsive and hazardous as it is, is perhaps the best we can hope for: a system which offers some kind of remission from constant armed assault. If this is the case within the nation state, there would also appear to be an argument for applying the principle to the community of nations.

The UN Security Council, which is the body charged with the enforcement of international law, is inherently tyrannical. It is tyrannical because, while it asserts a global monopoly of violence, we cannot peacefully remove and replace it. The veto powers possessed by its permanent members are a constitutional guarantee against reform: no change can be made without the consent of those whom we would seek to change. No one, at the international level, guards the guards.

It is, or should be, astonishing that, despite growing protests, so many of those who claim to support global justice appear to accept this dispensation. It is also interesting that the European right, which prides itself on resisting the impositions of the European Commission, not only submits to the tyranny of the Security Council and its strongest member, but actively supports it.

Two weeks ago, this column argued that, while the action being planned by the United States and Britain against Iraq is wholly unjust and must be resisted, it would be possible to conceive of a just war against its government, if the sole aim was to help the nation’s oppressed people deliver themselves from dictatorship, if the states prosecuting that war were not themselves the principal sources of global violence and had nothing to gain from invasion, and if the non-violent means of achieving the same outcome had first been exhausted.

The column provoked a storm of protest from pacifists, many of whom argued that there can be no such thing as a just war. David Edwards and David Cromwell, who run the website MediaLens, suggested that even the war against Hitler should not have been fought, on the grounds that it provoked the Holocaust. Quoting the historian Howard Zinn, they argued that "Germany’s anti-Semitic actions, cruel as they were, would not have turned to mass murder were it not for the psychic distortions of war, acting on already distorted minds."

Most of us would recognise this as a ridiculous evasion. This intellectual wriggling illustrates how hard it is to sustain the pacifist position in all circumstances. Indeed, many of those who claim to be against all war would, when pressed, agree that they recognise the right of the weak to defend themselves against the aggression of the strong. They would have supported the efforts of the Spanish republicans to resist Franco, of the Sandinista government to hold off the proxy warriors of the United States and of the rebel army in East Timor to seek to oust the occupying forces of Indonesia. They might also agree that such freedom fighters should not be left to struggle alone against far better-equipped opponents, but should be supported by international action. If so, if all other options were exhausted and if all the pre-conditions for a just war were met, it surely follows that we should also welcome an impartial attempt to help the rebels in Iraq to overthrow their dictator.

The problem is that the Security Council is constitutionally partisan. Its justice is the justice of the powerful, meted out against the weak. It will never act against the infractions of its permanent members or their closest allies. It will permit international action only when that action advances the interests of the dominant state. As a result, no war prosecuted by the UN Security Council can ever be considered just.

The world ideally needs a non-partisan police force, which is accountable to its people, and which would be just as prepared to prevent Israel’s oppression of the Palestinians or Turkey’s persecution of the Kurds as it is to prevent the atrocities perpetrated by the Iraqi government. The problem faced by such a body, however, is that if it sought to enforce a decision against any of the world’s well-resourced states – the US or Britain, for example – it would discover that, far from possessing a monopoly of violence, it was hopelessly outgunned. Indeed, a few months ago the US threatened to meet any attempt by the International Criminal Court to arrest its soldiers with greater violence. Yet if this police force were to accumulate enough weaponry to overwhelm the United States, it could acquire so much power that it would become oppressive in its own right.

It is not easy to see how we might resolve these problems. We could seek to establish alternative centres of power – the global parliament for which increasing numbers of activists are campaigning, for example – which could slowly leach authority from the existing international bodies. As America’s economic mismanagement reduces its global dominance, we could demand a security council which permits a better balance of power between nations. Tackling the permanent members’ constitutional veto is trickier; requiring, perhaps, a sustained revolt by many of their citizens. But these solutions must be sought, for without them there can be no just war, and no just peace.