This report discusses sovereign states' immunity from suits and attachments by U.S. nationals except under very specific circumstances, as well as legal interpretations and cases involving immunity rules. It particularly describes state-sponsored terrorism and the effect of The Justice Against Sponsors of Terrorism Act (JASTA), which was proposed to allow U.S. nationals to file civil suits in U.S. courts against foreign nations for aiding and abetting acts of terrorism under a new exception to the general rule of immunity.