International Law
State immunity, also known as sovereign immunity, is a principle of international law that shields a foreign state from the jurisdiction of domestic courts. It is rooted in the maxim par in parem non habet imperium—an equal has no power over an equal—and is recognized in both customary international law and treaties such as the 2004 United Nations Convention on Jurisdictional Immunities of States and Their Property. The doctrine distinguishes between acta jure imperii (sovereign acts) and acta jure gestionis (commercial acts), with most states now applying a restrictive theory that denies immunity for the latter.
The doctrine of absolute immunity prevailed in the 19th century, when states were generally immune from foreign jurisdiction in all matters. The shift toward restrictive immunity began in the early 20th century, notably with the 1926 Belgian Court of Cassation decision in Société anonyme des chemins de fer liégeois-luxembourgeois v. État néerlandais, which distinguished between sovereign and commercial acts. The 1952 Tate Letter issued by the US State Department endorsed the restrictive theory, and the 1976 Foreign Sovereign Immunities Act (FSIA) codified it in US law. The 1972 European Convention on State Immunity and the 2004 UN Convention further solidified the restrictive approach, although the latter has not yet entered into force.
Under the restrictive theory, immunity is denied for commercial transactions, but exceptions also exist for torts committed within the forum state, immovable property, and arbitration agreements. The UN Convention lists these exceptions in Articles 10–17, and the FSIA provides similar exceptions in 28 U.S.C. §§ 1605–1607. The act of state doctrine, though distinct, often overlaps with immunity in cases involving foreign sovereign conduct. A notable limitation is the jure imperii exception for military activities, which remains absolute in many jurisdictions.1
Modern litigation has tested the boundaries of immunity, particularly in cases of human rights abuses and terrorism. The US FSIA was amended in 2008 to allow suits against state sponsors of terrorism, leading to judgments such as Bank Markazi v. Peterson (2016), where the US Supreme Court upheld the seizure of Iranian assets. In Europe, the European Court of Human Rights in Jones v. United Kingdom (2014) upheld immunity for torture claims, citing the need for interstate comity.2 The International Court of Justice in Jurisdictional Immunities of the State (2012) affirmed that immunity is a procedural bar, not a substantive defense, and that it applies even to alleged violations of jus cogens norms.3
State immunity extends to state-owned enterprises and central banks, but with nuances: central bank assets are often immune from execution unless explicitly waived. The doctrine also applies to criminal jurisdiction, though heads of state enjoy personal immunity before international tribunals, as seen in the ICC’s arrest warrant for Omar al-Bashir.4 A rarely discussed facet is the immunity of state officials for official acts, which was addressed in the Yerodia case (ICJ 2002).3 Additionally, the UN Convention includes a provision on counterclaims, allowing a state to be sued on a counterclaim if it initiates proceedings.
State immunity remains a dynamic area of international law, balancing sovereign equality with accountability.
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