The ongoing war in Ukraine has, once again, raised the question of the rights and wrongs of military interventionism.
In discussing this topic, we should start off by noting that, when it comes to conflicts between states – entities which are unethical and unjust by definition – it is difficult to make neat categorisations between aggressor and victim. States are fundamentally aggressive by definition, and so it is difficult to talk about them as if we are discussing the rights and obligations that arise between private individuals and entities. As such, any acts by states can often be judged not in terms of right or wrong but only of what is better or worse for the freedom of the citizens who must suffer from their rule. In fact, the Russia/Ukraine/NATO conflict is an exemplar of this. Moreover, much interventionism that feigns to be defensive tends not to be so – the Iraq war being a prime, recent example.
However, if we ignore this complication by assuming that the assessment of a given situation provides a clear distinction between an aggressor state and a victim state, what can we say about interventionist efforts by third party, non-aggressing countries to either prevent or quash the act of aggression?
To be a libertarian is to believe that the initiation of force against the person or property against another is inherently unjust. This belief proscribes neither the right to self-defence of one’s person and property, nor the right to provide defence services towards someone else who is the victim of aggression. There are two key elaborations to make to this principle.
First, libertarianism itself does not state that someone must defend himself or rush to the defence of other people. One may, by another standard, incur a moral obligation to do so, but such an obligation cannot be enforced by the law, as this would itself breach the non-aggression principle. Indeed, one is perfectly entitled to live as a pacifist, eschewing any kind of force whatsoever. It is quite consistent, therefore, to state that someone should choose to aid a victim of aggressive violence but that he should not be forced to do so.
Second, if you do decide to respond to an act of aggression then you do not have the right to inflict aggressive violence on an innocent party in the process, either by forcing them to assist you or by making them the victims of so-called “collateral damage”. One would not, for instance, launch a nuclear warhead, slaughtering the population of an entire landmass, in order to neutralise a single murderer.
Knowing this, we can summarise the basic position libertarian position on these matters as follows:
No person has the right to initiate violence (aggression) against any other person in any circumstance;
Where a person is the victim of aggression he has the right to defend himself;
Where a person attempts to defend himself he has no right to initiate violence against innocents during the act of doing so, including their enforced participation and causing “collateral damage”;
Where a person attempts to defend himself, other people have no right to initiate violence against him in order to stop him from doing so;
A person has the right to solicit, contract with or otherwise co-operate with third parties in furnishing his defensive capabilities;
Third parties, likewise, have the right to provide their funds and resources towards defence, either through a negotiated contract (security services) or charitably;
Third parties providing defence services have no right to initiate force against innocents during the act of doing so; this includes forcing others to contribute towards the same, and causing “collateral damage”;
Where a third party provides defence services it not may be forcibly stopped from doing so by others;
Whether the injured party or a third party should or should not act to defend the former against an act of aggression, or whether such an act of defence is a “good” or “bad” thing by some other moral standard may be debated; however, the conclusion may not be enforced violently on any party that is not committing an act of aggression.
When it comes to the mainstream debate of the interventionist efforts of our governments, the question tends to be presented as all or nothing: should weall – via our government – intervene, or should weall not intervene. But, in light of the summary we have just outlined, there is a distinct problem with each of these holistic responses from a libertarian perspective.
Those who answer in the affirmative have rightly recognised that defensive force may be used in such a situation because the non-aggression principle has been violated by another party. However, they are overlooking the fact that the funds to be directed towards military intervention are extracted forcibly by the state through tax revenue – in other words, people are being forced to fund the interventionist venture. They are mistaking the right to intervene on the one hand with a violently enforceable obligation to do so on the other. But this violently enforceable obligation is itself a breach of the non-aggression principle, and is, therefore, anti-libertarian and unjust. These advocates of interventionism are most welcome to criticise other people from the point of view of moral standards that are separate from, but compatible with, libertarianism. Indeed they are most welcome to contribute their own legitimately earned wealth (if they have any) and that of anyone whom they can persuade to join them voluntarily in the venture towards defending the victim country. But what they do not have is the right to force other people to the same, either by extracting funding through taxes or by enforcing conscription.
Those, however, who answer in the negative – that we should not intervene – may recognise rightly that we cannot force people to participate in intervention. But now they seem to be making the opposite mistake of preventing people who want to intervene from doing so – especially if their justification for that denial is that there are “better” things that “our” taxes should be spent on. As we just mentioned, if someone is genuinely outraged by the infliction of violence (believing that his assistance against such heinous acts is a worthwhile devotion of his own funds) then he is quite within his rights to contribute those funds accordingly. In fact, he may even decide to join a voluntary defence force, providing personal support for the victims. To stop someone from doing this if that is what they want is as much an affront to the non-aggression principle as forcing their assistance if they are reluctant. Once again, we must emphasise that it may not be a good thing, by some standard exogenous to libertarianism (e.g. pacifist morality), for a person to engage in intervention; but that does not mean that this person may be violently prevented from doing so.
All of this points towards one conclusion: that, given the unjust nature of the way in which the state could carry out its interventionist efforts, states should never intervene overseas – even for ostensibly just and noble causes. Whether such causes should be either supported or ignored is a matter for each, private citizen.
Such an outcome is bolstered by the fact that “war is the health of the state”. Never matter the reason why it is carried out, war hands to the state on a silver platter every excuse it needs to swell its power through an almost limitless list of outlets: forced redirection of the economy towards the war effort overseen by vast bureaucracies (which often form the model for subsequent peacetime, bureaucratic management); censorship of the press and of speech; endless propaganda; the possibility of conscription; rationing of basic goods. All of this is before we even mention the direct effects of death and destruction that war brings in her wake. The avoidance of war is, therefore, one of the highest priorities for anyone keen on preserving the liberty of the individual.
Thus, from both a theoretical and a strategic perspective, libertarians can find little, if any, justification for the interventionist efforts of states, and they should be opposed in each circumstance.
 See here for a detailed explanation of these difficulties.
 The only exception to this rule is if the actions of an aggressor have made it reasonably impossible for the victim to take defensive actions without harming the third party. For instance, if P steals Q’s car to run over R, R is entitled to shoot at Q’s car in order to stop P. In this case, P, not R, would be responsible for compensating Q for the damage to the car. For a more detailed explanation of this, see part of this essay.