As is well known, the issue of war creates divides that cut across liberal, conservatives, and libertarian ranks.  Here I wish to focus on libertarian attitudes toward war. Most libertarians oppose foreign wars on the ground that the government does not have the right to use taxpayers’ money to fight for the freedoms of others. They therefore accept national defense but oppose all other foreign interventions, even if undertaken for a just cause. This position has nothing to do with respecting the sovereignty of other nations; rather, it rests on the principle of limited government. The government’s job is to defend us. It cannot use its coercive powers to defend or protect others, even if doing so would be otherwise justified.

Is this argument sound? What if defending us requires defending others? What are the limits of the use of military powers under a libertarian view of politics? Is there any room for duties of assistance, i.e. stopping genocide? Isn’t the libertarian objection overcome by the use of a voluntary army? Assuming (as most libertarians do) that conscription is inadmissible, does the social contract contain a clause that a voluntary army can only be used in self-defense? What is the moral difference between using tax dollars to fight a just war (with a voluntary army) and using those same dollars for peaceful foreign-policy purposes, given that the intrusion in the citizens’ liberty (their pockets) is the same?