There are five theories of criminal jurisdiction. The territorial theory allows for jurisdiction over conduct that occurs within the territorial boundaries of the state. The nationality theory bases jurisdiction on the allegiance or nationality of the perpetrator as prescribed by the state of allegiance no matter where an offense occurs. The protective principle emphasizes the effect or possible effect of the offense and provides for jurisdiction over conduct deemed harmful to specific national interests of the forum state. The passive personality principle extends jurisdiction over offenses where the victims are nationals of the forum state, and the universal theory allows jurisdiction in any forum that obtains jurisdiction over the perpetrators of offenses considered particularly heinous or harmful to mankind generally. It appears that the U.S. courts and the authors of the Restatement Draft of the Foreign Relations Law of the United States have developed the notion that jurisdiction may be asserted over cases of at least serious and nearly universally condemned extraterritorial conspiracies or other offenses as long as the offense was intended to have 'substantial effect' on the territory of the United States and as long as the assertion of jurisdiction is reasonable. When such an assertion is said to be based on the objective territorial principle, it is conceptually defective. It is more conceptually accurate to maintain that jurisdiction is based on a combination of notions underlying the protective principle and the objective territorial and universality theories. A total of 189 footnotes are provided.