Prompted by cases questioning the legality of detentions at Guantanamo Bay, the Supreme Court recently considered fundamentally important questions regarding extraterritorial application of the US Constitution. There is over a century?s worth of case law on this subject, however there are several competing interpretations of these cases. The three most prominent schools of jurisprudence on extraterritoriality are functionalism, which aims to extend the constitution on a case-by-case basis, globalism, which advocates universal application of the constitution without reservation, and strict-territorialism, which supports adjudication using the constitution only where the US is the lawful sovereign. I ultimately endorse the functional standard, represented by the ?Impracticable and Anomalous? test. The ?Impracticable and Anomalous? test seeks to evaluate whether or not the relationship between the person seeking constitutional protections and the US merits extension of the constitution extraterritorially. Despite criticisms that functionalism is too subjective to determine when the constitution applies outside of De Jure US territories, I argue that the court in Boumediene v. Bush sufficiently clarified the scope of the functional standard by refining the parameters for extraterritorial applicability. The court carefully considered the specific facts of each case in determining whether the constitution should be applied abroad, which is itself testament to the need for the functional, albeit somewhat subjective standard.