1. One should be aware that ‘the libertarian argument’ does not equal ‘comments about US foreign policy’. Libertarianism should be a theory for all people everywhere. Much of the debate on foreign policy among libertarians is about American foreign policy. The US however is the exception, in terms of capacity, defense budget, possible reach of its military operations, the number of military alliances, et cetera. One cannot just say ‘smaller defence’ is better for all countries, as this would entail that many small countries would not be able to defend themselves, and indeed many are not. Even most (rich) West European countries are unable to defend themselves without NATO.
This is not to say one should not criticize US foreign policy decisions, or argue against particular military interventions abroad. It does call for further thinking among libertarians about the position of a great power in world politics. I think, particular in a globalized world, it is too simple to say such a power should retreat as much as possible from international affairs. A power vacuum will be filled, and there is no guarantee this will be beneficial to the US or the West. Indeed, I suspect it will not be.
2. Also, there is not one ‘libertarian idea about international relations’, here it is useful and needed to distinguish a separate classical liberal position, as I have argued in my book on classical liberalism and international relations theory (see the covers to the right) and will further elaborate in Degrees of Freedom, my next book that will be published next year with Transaction Publishers. There are many differences, but a main one in this context is that libertarians argue for defense as self-defense, while classical liberals accept that countries are part of international society of states, which demands a more active role in some areas. Not least a role in maintaining a regional or global balance of power. I think that is completely in line with Hayekian ideas about sponataneous order (pdf).
3. Libertarians lack meaningful thoughts about the dynamics of a world which would (partly) be characterized by libertarian ideas. Most will accept that a peaceful paradise is unlikely to unfold, yet do not think much about the alternative situations. This gap must be filled to make the basic argument more convincing (or not of course).