State Sponsors of Terrorism do not typically maintain significant assets in the United States.
Therefore, the main option for judgment holders against Iran, Syria and Sudan is to attempt to enforce their FSIA judgments in countries where these governments do maintain significant assets. Unfortunately, these efforts are often unsuccessful.
For example, in October 2015, the Italian Court of Cassation refused to enforce an FSIA judgment against Iran. The Italian court held that although acts of terrorism are not entitled to immunity, to be recognized, a foreign judgment must accord with Italian jurisdictional principles and since the claims could not have been brought under Italian law, the American judgment could not be enforced in Italy.
Even in the U.S., enforcement actions have frequently run into the teeth of long-held principles of sovereign immunity.
For example, in 2016, the Seventh Circuit Court of Appeals held that plaintiffs holding judgments under the FSIA’s Terrorism Exception were not necessarily entitled to collect on those judgments by seizing Iranian assets, and were required to first overcome other hurdles to attach sovereign assets.