Scores of federal criminal and civil statutes are “geoambiguous”—they do not say whether they apply to conduct that takes place in foreign countries. This is a vital concern in an age of exploding globalization. The Supreme Court regularly cites a “presumption against extraterritoriality,” but just as often overlooks it and opts to apply geoambiguous law abroad. The Court’s inconsistency bespeaks a deep divide among scholars. Judicial unilateralists favor liberally imposing U.S. law abroad to respond to unwanted effects from foreign conduct. Judicial territorialists favor restraint and a return to traditional territoriality to avoid international conflict. And judicial interests balancers favor multi-factored, case-by-case consideration of whether it is “reasonable” to apply geoambiguous law abroad.
The Article advances a new approach—a proposed rule of “dual illegality” to govern how courts apply geoambiguous laws. Under a dual-illegality rule, U.S. courts should decline to apply geoambiguous laws to penalize or regulate conduct that occurs in the territory of a foreign state unless the same conduct is also illegal or similarly regulated by the law of the foreign territorial state. A similar rule of dual illegality has worked for many decades as a limitation in countless criminal extradition treaties. A dual-illegality rule would revitalize traditional territoriality values as a limiting principle on U.S. assertion of its law abroad, while also allowing extraterritoriality when there is the least likelihood of provoking political dispute. The response to greater globalization should be less jurisdictional contestability and more reliance on rules that do not invite judges—as the rules wrongly do now—to engage in policy-like assessments of the needs or interests of the United States in having its law applied to activity abroad. Courts should apply a dual-illegality rule to decide the scope of geoambiguous law.