Definition
A Latin maxim meaning "by the right of war" or "by the law of war." The phrase operates as a legal justification or basis of authority — acts done, rights acquired, or property seized *jure belli* are done under the authority and sanction of the laws of war, as distinct from acts grounded in municipal law, treaty, or peacetime legal process. It appears most frequently in the law of nations (international law) and in prize law, where the right to capture enemy property at sea is treated as derived from the law of war itself rather than from the domestic law of any sovereign.
Why It Matters in Research
This is a term of art from the classical law of nations tradition, most at home in admiralty and prize court literature. Researchers encountering *jure belli* in historical sources should understand it as a signal that the writer is grounding a claim or authority in the law of war as a body of international law — not in a statute, treaty, or common law rule. The phrase typically answers the question: *by what right?*
The term appears in admiralty decisions involving prize — the capture of enemy ships and cargo during wartime. Prize courts, including the British High Court of Admiralty, regularly invoked *jure belli* to distinguish lawful captures from piracy or unauthorized seizure. When Christopher Robinson's *Admiralty Reports* (cited by both Black's and Burrill's) reference the term, the context is almost invariably prize jurisdiction and the rights of belligerents over enemy and neutral property.
In American sources, James Kent's *Commentaries on American Law* (also cited in the historical entries) situates *jure belli* within the broader law of nations as received into American legal thought in the early nineteenth century. Researchers working in this corpus should trace the phrase through the prize law tradition and international law treatises rather than expecting to find it developed in case law dealing with domestic property or contract.
A trap for researchers: *jure belli* does not appear in modern statutory or regulatory sources with any frequency. Its natural habitat is pre-twentieth-century admiralty opinions, treatises on the law of nations, and works on belligerent rights. Searching for it in contemporary materials will yield little; its analytical work has largely been absorbed into the vocabulary of international humanitarian law and the law of armed conflict.
Historical Dictionary Support
The three source dictionaries are in complete agreement on the translation — "by the right, or law, of war" — and all three point to the same pair of authorities: Kent's *Commentaries* (volume 1, page 126) and Robinson's *Admiralty Reports* (volume 1, page 289). This convergence confirms that the term's principal usage in Anglo-American legal literature was tied to prize law and the law of nations rather than to any domestic legal context. None of the historical dictionaries elaborate on the substantive doctrine; they treat the phrase as a term of reference whose meaning is supplied by the treatise and admiralty literature they cite. Researchers who need the substance must go to those underlying sources. The brevity of all three entries reflects the term's function: it is a doctrinal shorthand used in contexts where the reader was presumed to be familiar with the law of nations tradition.
Jurisdictional Note
*Jure belli* is a concept of international law and admiralty rather than domestic law, so ordinary jurisdictional variation between American states is not relevant. The operative distinctions are between municipal law and the law of nations, and between belligerent and neutral status under international law. Prize jurisdiction in the United States is vested exclusively in federal courts.