Members of the community of nations have traditionally accorded a variety of immunities to foreign sovereigns, their representatives and instrumentalities, and their property. The roots of these immunities are buried deep in history. After centuries of evolution and institutionalization by public international law and the internal laws of the members of the community of nations, one may speak of a generic idea of sovereign immunity that has various manifestations. The foundation of foreign sovereign immunity remains a disputed matter. According to one view, the members of the international community are bound by customary public international law to accord immunity to foreign sovereigns because of their equality and independence; a refusal to do so is a breach of an international obligation. According to another view, foreign sovereign immunity is founded on comity. In the absence of an international treaty, members of the international community are in no way bound to accord immunity to a foreign sovereign; if they do so, it is by virtue of internal rules of law. All agree, however, that the purpose of foreign sovereign immunity is to avoid friction in international relations.
Whether under compulsion from public international law, internal law, or both, ships of foreign sovereigns traditionally have been accorded certain immunities. Ships are property, though of a special kind, and have enjoyed the immunity from arrest and execution that is accorded to the property of a foreign sovereign. Further, ships have been personified for a number of purposes in the United States and in other countries and have been accorded an immunity that resembles the immunity accorded to the person of a foreign sovereign.
This paper will comment on the laws of the United States that govern the immunity of foreign state-owned ships from arrest for the enforcement of maritime claims in American courts. A ship is entitled to a species of immunity that is distinct from the immunity accorded to the person or the property of a foreign sovereign. The origin and development of this immunity will be traced in Anglo-American judicial decisions and other sources of law, and the provisions of the Foreign Sovereign Immunities Act of the United States will be discussed to the extent that they are pertinent to the enforcement of maritime claims. For purposes of comparison, and for the elucidation of a number of problems, brief reference will be made to international conventions and the internal laws of other countries.