A brief precis:
At the time of the drafting of the Constitution, there were four truly effective navies in the world: the British, Dutch, French and Spanish.
One of the things that the US Constitution specifically authorized and which the Founders saw as very necessary (the Federalist discusses this at length) was the creation of an American navy so the new republic would not be at the mercy of powerful European navies that could blockade US ports and harass US commercial shipping.
However, the Founders were not dreamers: they knew that it would take years for the US to establish a navy that could hold its own against any one of the Great Powers, let alone challenge them.
Of course, even the Great Powers were hamstrung by technology: once a ship had sailed onto the high seas, there was no way for them to communicate with one another, and there was no way for their navies to be everywhere. To supplement their naval reach, the governments of Europe had begun issuing letters of marque and reprisal centuries before. Essentially, the captain and crew of private commercial vessels could obtain these letters from a government that wanted to increase the size of its fleet without spending money to build new warships. The letters entitled their bearer to essentially act as a pirate - the most famous bearer of such letters was Sir Walter Raleigh. The bearers would prey upon the shipping of the issuer of the letters' enemies. British letter bearers would harass Spanish or French shipping, etc. If the bearers were captured by the enemy, they could claim to be prisoners of war subject to the laws of war and not common criminals. If the bearers were captured attacking the shipping of one country while in a third country's territorial waters, they could claim to be acting on behalf of the letter-issuing government and therefore subject to deportation, not prosecution or worse, extradition to the country whose shipping they were attacking.
The letter bearers got to keep some or all of the goods and vessels they captured, depending on the terms they negotiated.
The fledging US government authorized such letters in the Constitution as a way to cheaply raise and supplement a fleet while building a national navy.
During the Barbary Wars and the War of 1812, a good number of letters were issued.
But in 1856, the Great Powers abolished such letters at the Treaty Of Paris - which meant that the world's great navies would henceforth uniformly consider such letter bearers pirates and summarily hang them when found.
As a result it was not worthwhile for any country to issue such letters, as they were unenforceable and carried no protection.
In the wake of the Geneva Convention they are now completely useless.
In any case, Bin Laden is not be found on the high seas.
But I have no reason to believe that he cynically advocated the letters of marque, knowing in advance they wouldn't work.
I do, since he already voted to authorize War in Afghanistan before he floated this silly idea.
Re your pertinent point that Paul "already voted to authorize War in Afghanistan before he floated this silly idea", he didn't see the two as mutually exclusive:
Today, we have a new type of deadly piracy, in the high sky over our country. The solution the founders came up with under these circumstances was for Congress to grant letters of marque and reprisal. This puts the responsibility in the hands of Congress to direct the President to perform a task with permission to use and reward private sources to carry out the task, such as the elimination of Osama bin Laden and his key supporters. This allows narrow targeting of the enemy. This effort would not preclude the president's other efforts to resolve the crisis, but if successful would preclude a foolish invasion of a remote country with a forbidding terrain like Afghanistan- a country that no foreign power has ever conquered throughout all of history.
http://www.house.gov/paul/congrec/congrec2001/cr092501.htm
In any case, Bin Laden is not be found on the high seas.
Good point. The meaning of LM&R would apparently have expanded with Congress' adoption of Paul's suggestion.
Perhaps "bounty" fits better the reasoning of Paul:
Conventional armed forces are ill-suited to tracking down international terrorists. Our military invasion of Afghanistan undoubtedly has scattered al-Qaida throughout the Middle East and Europe. Marque and reprisal would create an incentive for individuals close to bin Laden to kill or capture him and his associates. This method in effect places a bounty on the heads of international terrorists, who often travel between countries, melt into civilian populations, or hide in remote areas. The goal is to avail ourselves of the knowledge and expertise of private parties, especially given the lack of western intelligence in many of the countries likely to harbor bin Laden. Marque and reprisal could turn the tables on the terrorists, forcing them to live as marked men. Terrorist should fear us, not the other way around.
http://www.ronpaul2008.com/articles/111/will-we-bring-bin-laden-to-justice/