It's an interesting question presented in a cert petition filed in the Supreme Court. It's especially problematic when Congress fails to address the extraterritorial reach of a statute. Some courts look to international principles and use an "effects" test.  But in this day and age, what doesn't affect the US?  I have written articles on the extraterritorial prosecution of white collar crimes (here), computer crimes (here), and business crimes ("Defensive Territoriality": A New Paradigm for the Prosecution of Extraterritorial Business Crimes, 31 Georgia Journal International & Comparative Law 1 (2003)),

See British American Tobacco (Investments) Limited v. U.S. – Download BATCo Cert Petition and Appendix

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