As explained, it's an old fashioned bounty on their heads. Govts did this in the days of priacy, hiring private ships and crews to hunt down the pirate ships and kill them and their crews or bring them back home to decorate a ships yardarm.
The Constitution specifically allows the government to issue Letters of Marque for situations where a full military response isn't necessarily appropriate. We have companies in this country that are all former seals, special forces, army rangers etc that make VERY capable mercenaries. Mercenaries to hunt down Mercenaries :)
Godspeed
Just kiddin' (only partially). I can't remember back so far as my Catholic elementary school days enough to be able to tell you exactly about the term, but it is pronounced as "mark" (not "mar-kay").
The express power to "grant letters of marque and reprisal"... is often a measure of peace, to prevent the necessity of a resort to war. Thus, individuals of a nation sometimes suffer from the depredations of foreign potentates; and yet it may not be deemed either expedient or necessary to redress such grievances by a general declaration of war. Under such circumstances the law of nations authorizes the sovereign of the injured individual to grant him this mode of redress, whenever justice is denied to him by the state, to which the party, who has done the injury, belongs. In this case the letters of marque and reprisal...contain an authority to seize the bodies or goods of the subjects of the offending state, wherever they may be found, until satisfaction is made for the injury...
Put "marque and reprisal" into Google search engine and you should get numerous pages that will describe them for you. This is also a good way to research things before you type in a "stoopid" qwestion that can be quickly answered by a short search on the internet. (Ain't computers wunnerful?)
Contrary to Mr. Sinkspur's ignorant view, the Constitution- where the "letters of marque and reprisal" are contained- is not a "living document", but one of the most superbly crafted and thought out pieces of ideology that has been created in the history of the world. If it is written in the Constitution, I have found that there is usually a d*mn good reason for it and idiots who poo-poo it usually have brown eyes (due to where their head is usually positioned.)
It may be a tritely worded and seemingly anachronistic idea -letters of marque and reprisal, that is- but I have the feeling that it still will serve its purpose exceedingly well for our Country.
"History repeats itself; it has to, nobody ever listens"
To the others, I doubt this is about mercenaries in Afghanistan. Someone with a letter of marque and reprisal against al Qaeda (and its allies, hopefully) might be able to get away with targetting them anywhere. And they could be informally told to go into Iran or some other problem country we aren't officially messing with over this yet, do their thing, and we could claim they're acting outside the letter while doing nothing about it.
I would like letters of marque and reprisal to be available, but I'm not brave enough to try acting under one. And whoever has them will have the nightmare of infiltrating countries where the people look different and speak different languages.