I have seen absolutely nothing on Letters Of Marque so I would only be guessing. However, the 25 million dollar reward on Bin Laden’s head dead or alive seems to be similar wouldn't you say?
Sort of similar, except that Letters of Marque and Reprisal are for the purpose of seizing the merchant ships of enemy nations.
To put out a reward for bin Laden would not require a Letter of Marque or Reprisal, and I don't think such a Letter would truly apply in this case, since bin Laden's not a merchant ship or a nation.
On the other hand, 25 mil is tempting, and if I were younger and in a "Soldier of Fortune" frame of mind, hells bells, 25 mil could come in handy. ;-)
I wonder if 25 FReepers would want to go in for 1 mil apiece and go over there and bring back that terrorist bastard's head on a pike. Fantasies....