Criminal law is usually territorial. It is a matter of the law of the place where it occurs. Nevertheless, a number of American criminal laws apply extraterritorially outside of the United States. Application is generally a question of legislative intent, express or implied. There are two exceptions. First, the statute must come within Congress's constitutional authority to enact. Second, neither the statute nor its application may violate due process or any other constitutional prohibition. Claims of implied extraterritoriality must overcome additional obstacles. Federal laws are presumed to apply only within the United States, unless Congress clearly provides otherwise. Moreover, the courts will also presume that Congress intends its statutes to be applied in a manner that does not offend international law. Historically, in order to overcome these presumptions, the lower federal courts have read certain vintage Supreme Court cases broadly. The Supreme Court's recent pronouncements in Morrison v. National Australia Bank Ltd. and RJR Nabisco v. European Community, however, suggest a far more restrictive view. Although the crimes over which the United States has extraterritorial jurisdiction may be many, so are the obstacles to their enforcement. For both practical and diplomatic reasons, criminal investigations within another country require the acquiescence, consent, or preferably the assistance, of the authorities of the host country. The United States has mutual legal assistance treaties with several countries designed to formalize such cooperative law enforcement assistance. It has agreements for the same purpose in many other instances. Cooperation, however, may introduce new obstacles. Searches and interrogations carried out jointly with foreign officials, certainly if they involve Americans, must be conducted within the confines of the Fourth and Fifth Amendments. And the Sixth Amendment imposes limits upon the use in American criminal trials of depositions taken abroad. The nation's recently negotiated extradition treaties address some of the features of earlier agreements which complicate extradition for extraterritorial offenses, that is, dual criminality requirements; reluctance to recognize extraterritorial jurisdiction; and exemptions on the basis of nationality or political offenses. To further facilitate the prosecution of federal crimes with extraterritorial application Congress has enacted special venue, statute of limitations, and evidentiary statutes. To further cooperative efforts, it enacted the Foreign Evidence Request Efficiency Act, P.L. 111-79, which authorizes federal courts to issue search warrants, subpoenas, and other orders to facilitate criminal investigations in this country on behalf of foreign law enforcement officials.