The United Nations has bumbled for more than 40 years in trying to come up with a definition of terrorism, creating a legal black hole that's allowed some nations to harbor terrorists by declaring them 'freedom fighters' and let the United States sweep up 'enemy combatants' with impunity.

The definition's been elusive because terrorists are neither state-actors nor common criminals, a 'strangely hybrid status' the international community's been unable to grasp, Douglas R. Burgess Jr. writes in Legal Affairs. It shouldn't be though -- it's the same legal category used for pirates for more than 100 years.

It may seem a clever, albeit unenlightening observation, but the history of piracy and the war against it offer some helpful lessons for today's botched legal and military efforts against terrorism. Both groups function as extraterritorial bands of disenfranchised men who use terrifying tactics to advance their agendas. Both have given rise to 'wars' between states and non-state actors.

Like terrorists, pirates once functioned as adjuncts for states' dirty work. Queen Elizabeth granted 'letters of marque' to pirates who terrorized the coast of Spain, while she maintained a public appearance of appall at their actions. But pirates proved difficult to control, and the threat they posed to countries grew. The history 'bears chilling similarity to current state-sponsored terrorism,' Burgess writes. One need only look to Afghanistan, where the United States trained the mujahadeen against the Soviets in the 1980s.

An international resolve to stamp out piracy was realized with the Declaration of Paris in 1856, when piracy was deemed an illegitimate use of state power. It was the first time international law stretched beyond the categories of people and states and it set the stage for subsequent UN conventions that put pirates under universal jurisdiction, meaning they can be tried anywhere by any nation that catches them.