Ok, so I bring up the seemingly fanciful idea of going to fight pirates under a Letter of Marque and Reprisal. What sort of legal background hurdles actually stand in the way of a private individual hellbent on heading to the high seas off the Horn of Africa?
Interestingly, Ron Paul introduced legislation in 2001 to authorize the seemingly moribund concept of Letters of Marque and Reprisal against Osama bin Laden. He sought to use Congress's Constitutional authority to grant the President the power to authorize private individuals to pursue bin Laden under such Letters. He pushed the bill again in 2007. Here's the text.
Congress also has the enumerated Article I, Section 8 power to "define and punish piracies and felonies committed on the high seas" and the power to "make rules concerning captures on land and water."
While the U.S. refused to sign the 1856 Paris Declaration by which signatories agreed to cease issuing authorization to privateers, it basically respected it during the Civil War and the Spanish-American War. However, during World War II, the U.S. Navy granted a Letter of Marque to an anti-submarine airship in the Pacific.
Today, it seems unclear whether international legal norms over time, rooted in the Paris Declaration and the subsequent 1907 Hague Convention, would constitute sufficient customary international law be found to hold privateering illegal in the eyes of a U.S. court. It appears to be illegal under U.S. Code for a U.S. citizen to "cruise" as a privateer against U.S. citizens and their property. But I haven't researched in depth about how the Congress would actually go about granting a Letter of Marque and Reprisal under the present legislative paradigm.
ADDED: A little bleg - Can privateers be authorized against irregular pirates or are letters of marque limited to authorizing capture of vessels connected to a specific foreign power party?
ADDED: Does a private individual even require authorization in the form of a Letter of Marque and Reprisal to "cruise" as a privateer against non-state-backed pirates on the high seas? Or can anyone capture them at any time? One learned treatise observes:
"International law authorizes the capture on the high seas of pirates at all times [...]."
But there's the UNCLOS treaty...which the U.S. has not signed, but might be held nevertheless as customary international law binding in U.S. courts. From Part VII, Article 107 0f that treaty on the law of the sea (indicating a need for authorization by a state for private individuals to capture pirates):
Ships and aircraft which are entitled to seize on account of piracy
A seizure on account of piracy may be carried out only by warships or military aircraft, or other ships or aircraft clearly marked and identifiable as being on government service and authorized to that effect.