Status of Forces Agreement (SOFA): What is it, and How has it been Utilized
http://www.fas.org/sgp/crs/natsec/RL34531.pdf
SOFAs are bilateral or multilateral agreements that establish the legal framework under which U.S. military personnel operate in a foreign country and whether domestic laws of the foreign jurisdiction apply to U.S. personnel in that country. The killing of Afghan civilians, allegedly by a U.S. soldier, has raised questions regarding the SOFA in place between Afghanistan and the U.S. and who would prosecute the service member. From the Congressional Research Service, posted by the Federation of American Scientists