There is an interesting debate now underway between two of the moderators of the popular Bleeding Heart Libertarians site, who also happen to be co-authors of a book on the morality of humanitarian military interventions. One author, Professor Teson, takes the view that such intercessions are permissible if they are in support of a just cause; if the harmful consequences of the military strike are proportional to the number of innocent lives at risk; and if the leader(s) authorizing the intervention have soberly and in good faith attempted to calculate the costs and benefits of their actions. Professor van der Vossen, in contrast, holds that the track record of such intercessions is so poor that Teson’s second condition can almost never be satisfied.
This is a timely and well-reasoned debate on an important ethical issue, and certainly worth reading. For the reasons outlined in my comments on the second of van der Vossen’s posts, I side with Teson. However, this piece is directed towards a separate, distinctly libertarian objection to humanitarian interventions. That is, even if we accept that such measures may sometimes satisfy Teson’s conditions, they are still impermissible because financed by coercive means.
For most libertarians, even noble ends should not be advanced by ignoble means. Of course, the state should defend us from invasion or direct attack, but if US citizens wish to help the oppressed in far-off lands, they should contribute their own resources or services. However, I believe this objection loses some of its punch if we focus more closely on the nature of “humanitarian” interventions.
At least for purposes of this debate, Teson recognizes two species of potentially permissible military engagement: “A war is just if, and only if, it is in defense of persons. If it is a war in defense of my compatriots it is called national self-defense. If it is a war in defense of others it is called humanitarian intervention. The United States government did not conduct the Syria strikes to defend Americans, so it was not a war in self-defense.” However, unless Teson is using “defense of persons” in an extraordinary broad and unnatural way, this taxonomy seems incomplete.
There exists a third rationale of just military engagements, i.e. those fought by states not in defense of countrymen as such, but in defense of their rights. Our entry into WWI is arguably a prominent example. Germany and her allies were not realistically threatening an invasion of the US, but were using military force to sink our merchant ships and thus block our trade with the UK and other friendly nations.
Of course, not every violation of national rights warrants the carnage of a full-scale war, but it should be clear that this sort of infringement may justify a resort to force. Consider the following thought experiment. You live in a Lockean state of nature, meaning that individuals enforce their own rights as they see fit or organize groups for this purpose. In this environment, you socialize and exchange goods with another person, whom we may call “Joe.” You visit his residence and he visits yours for pleasure, and you regularly exchange goods or services. Occasionally you invest in his projects. All of this is done willingly and for mutual advantage.
On one such visit to Joe, you are met at the door by “Sam,” who informs you that he now determines who may visit or exchange with Joe, and that you are no longer permitted to do so. You inform Sam that this arrangement is unacceptable to you, and that you insist on seeing your friend. We may suppose that you have mixed motives for this stance. You both have concerns for Joe’s well-being, while simultaneously deriving a substantial material benefit from your business relationship. You also fear that if you submit to Sam here, he will pull the same stunt with other friends of yours.
Thus, you ask Sam to please step aside. He refuses. You then attempt to push past Sam, who pulls out a weapon. You struggle with him, and he is mortally wounded. It seems obvious that you are not in the least bit culpable for Sam’s death. And because the only legitimate purpose of the minimal state is to vindicate its citizens’ (libertarian) rights, its leaders would be justified in acting in a comparable way on behalf of their citizens, in analogous circumstances.
The point is that for the contemporary US there would rarely if ever be a purely humanitarian intervention. Our firms have commercial relationships and our citizens have family and friends in every corner of the world. Aggression against innocent persons, whether by an external power or by a tyrant against his own population, endangers these legitimate interests. Moreover, as noted above, successful aggression may be repeated elsewhere. Therefore, any military engagement other than to repel an invasion of the homeland, will be an admixture of selfish and altruistic concerns.
Of course, there are potential interventions where one motivation or the other would clearly dominate. In cases where the motivation is primarily altruistic, the libertarian objection remains unrequited. Nevertheless, there will certainly be mixed cases, in which both elements are present, and neither overshadows the other. This fact may present policy-makers with a little more latitude for permissible intervention than recognized by libertarian orthodoxy.
 I know that Teson is aware of this objection, but it is not addressed in the referenced debate.
 Van der Vossen does not contest or criticize this classification.