Mercenaries and the Libertarian State

I found myself wondering recently whether a libertarian country would allow its citizens to hire mercenaries to fight abroad.

Most libertarians believe in non-intervention, and many think that America (even Britain) should have stayed out of WWI (even WWII).

So if Britain had been a libertarian state in 1939, which decided to leave the continentals to their fate, or an isolationist America had likewise avoided conflict with Japan, and kept out of WII, should citizens of those countries have been free to fund mercenaries to fight against the Axis? Would this be morally different from hiring a hit-man or violent mob at home?

A quick search turned up a good article by Brian Micklethwait for the Libertarian Alliance, written shortly after the Falklands War. It opens with a quote from the back of The Whores of War (by Wilfred Burchett and Derek Roebuck, Pelican Special, 1977), which expresses the conventional view of mercenaries ("'whores' and 'sordid' ... people for whom the label 'soldiers of fortune' is a 'romantic misnomer'"). Micklethwait questions this view,

Part of the argument about whether the mercenary method of fighting a battle is good or wicked concerns the goodness or wickedness of the battle. But much also depends on how the warriors in it were recruited. Are they volunteers? Or were they press-ganged?

Recent events in the South Atlantic confirm how much better at fighting volunteer professionals are compared to conscripts, but that is beside the point I’m making here, which concerns the morals of the thing. Does the anonymous Pelican blurbsmith think that for the Argentine regime to coerce baffled teenagers into uniform was morally superior to enticing them into uniform with decent wages and generous widows benefits?

Though it doesn't address all of my questions, it's an interesting article, and well worth reading.