A very interesting report just published which, while explaining to a Congressional Committee about the legal status of certain small U.S. possessions and territories, touches on differences in the application of U.S. law and citizenship in these areas. Interestingly, "The Constitution does not apply in its entirety to territories solely by virtue of the fact that those territories have come under the possession and control of the United States. Whether rights under the Constitution apply to a territory and, if so, to what extent depends essentially on either of two factors, according to a series of Supreme Court decisions called the Insular Cases.15 The first is whether the right in question is considered to be "fundamental" or not; the second is whether the Congress has taken legislative action to extend the Constitution to the territory." In particular, federal income tax does not apply to many of these possessions (e.g., Saipan) and have become tax havens for some U.S. citizens. - U.S. Insular Areas: Application of the U.S. Constitution. OGC-98-5. 13 pp. plus 7 appendices (58 pp.) November 7, 1997. http://www.gao.gov/new.items/og98005.pdf