Phil Carter points out that the Patriot Act usefully expands US criminal law jurisdiction to sweep in “crimes committed by or against any U.S. national on lands or facilities designated for use by the United States government”:
Sure enough, Sec. 804 of the USA PATRIOT Act … amends 18 U.S.C. 7, also known as the “special maritime and territorial jurisdiction” statute of federal criminal law, to include U.S. military bases and embassies outside of the U.S. Here's the relevant text of 18 U.S.C. 7
Of course, this is of no great value to parties wishing to file civil law suits, and the odds that a US Attorney is going to start investigating Guantanamo seem pretty low. Prosecutions at Abu Ghrabi are firmly in the hands of the military justice system, and it's too soon to tell whether the military honor reflex or the military cover-up reflex will dominate.
But, as noted on Intel Dump, this amendment has borne fruit in the prosecution of a civilian contractor in Iraq for an assault that lead to the death of a CIA detainee. Update: Washiington Post explains the background to the prosecution.