On October 23, 1983, 241 U.S. Servicemen serving as civilian peace keepers in Beirut, Lebanon were killed when two converted water tankers loaded with explosives were detonated next two the barracks where the servicemen slept. This attack was the single deadliest terror attack on American citizens prior to 9/11.
The attack was perpetrated by the terrorist organization Hezbollah and funded by the Islamic Republic of Iran. The families of the victims of this attack eventually obtained a $2.6 billion judgment against Iran for its involvement in the attacks.
The families of the victims sought to collect their judgment by levying on the shipping companies which conducted business with Iran. In response to these levies, the shipping companies raised the sovereign immunity of Iran as a shield to not comply.
The trial court found that rather than being an affirmative defense which could only be raised by Iran, the issue of sovereign immunity could be raised sua sponte by the court.
In a 2-1 decision, The 9th Circuit upheld the decision of the trial court. Read the 9th Circuit Court of Appeals Decision Here