International law, it might be argued, is a legal system directed toward the defeat or suppression of a category of violators known as “enemies of mankind,” or hosti humanis generis. Sometimes these are war criminals, sometimes they are terrorists or slave traders. The original enemy of mankind was the “pirate.” Piracy gave rise to a highly specialized form of international jurisdiction known as universal jurisdiction. Because pirates were a threat to the global order (particularly global sea trade), or because they committed particularly heinous acts, or because their acts were committed in a place beyond the territorial jurisdiction or sovereignty of any state (different reasons have been adduced at different times), they were subject to the jurisdiction of any state that happened to identify them, engage with them, and capture them. Thus, a pirate could be prosecuted in every state’s courts. The contemporary law of piracy, embodied in the United Nations Convention on the Law of the Sea, has defined piracy as an act of violence or depredation committed on the high seas by a private actor acting for private ends. This distinguishes piracy from naval warfare or recognized belligerency on the high seas, but it has complicated efforts to apply the law of piracy to terrorists (who, after all, act for political ends, and most commonly in the territory of sovereign states) and it has meant that acts of piracy committed in the territorial waters of states are not subject to the international law of piracy (and the expansive forms of jurisdiction that accompany it). Therefore, attempts to assimilate terrorism to piracy have fallen foul of the technical rules governing traditional piracy. Likewise, these same rules frustrated initial efforts to confront the growing problem of traditional piracy carried out in places other than the high seas. The “international terrorist” and the Somali pirate, then, pose different problems for international law. In the case of terrorists, states have adopted ad hoc and controversial methods comparable to those used against pirates on the high seas. In the case of Somalia, the UN Security Council has authorized an international naval response to pirate attacks that permits foreign naval vessels to use force against pirates within Somali territorial waters.
As Condições para uma Paz Duradoura. Uma Leitura de "A Paz pelo Direito", de Hans Kelsen