Definition
Jure naturae (also rendered jure naturæ) is a Latin maxim meaning "by the law of nature" or "according to the law of nature." It appears in legal texts as a foundational phrase invoking natural law — the body of principles thought to be universal, pre-political, and binding on all persons by reason alone, independent of any enacted statute or sovereign command.
The phrase does not name a doctrine with specific elements so much as it invokes an underlying jurisprudential authority. When a legal conclusion is said to follow jure naturae, the claim is that the rule derives not from positive law (legislation, custom, or judicial decision) but from reason and the nature of human relations themselves.
The maxim most closely associated with the phrase is: Jure naturæ æquum est neminem cum alterius detrimento et injuria fieri locupletiorem — "According to the law of nature, it is just that no man should be made richer by the loss and injury of another." This principle, drawn from the Digest of Justinian (Dig. 50.17.206), is among the foundational statements of unjust enrichment in the Western legal tradition.
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Common Language
Modern common usage (Wiktionary): No entry. The phrase has no meaningful presence in modern ordinary English.
Historical common usage (Webster's 1913): Not separately defined. "Nature" and "natural law" appear broadly in philosophical and theological contexts.
The phrase is pure legal Latin with no common English counterpart. No COMMON LANGUAGE section applies.
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Why It Matters in Research
Researchers encounter jure naturae most often in two contexts: (1) historical treatises and common law opinions grounding equitable obligations — particularly quasi-contract and unjust enrichment — in natural law reasoning; and (2) Roman law sources and their reception into English and civil law systems.
The maxim from Dig. 50.17.206, reproduced in Burrill, is the single most important doctrinal thread to follow. It became a standard citation in early English equity and common law discussions of assumpsit, implied obligations, and restitution. When you find jure naturae in an older English case or treatise, the argument being made is almost always that an obligation exists without a formal contract — that equity or conscience supplies what positive law does not.
The critical research trap: in modern sources, jure naturae rarely appears by name. Its substantive content — no one should profit at another's expense — has migrated entirely into the modern law of unjust enrichment and restitution. Researchers who encounter the phrase in 17th- or 18th-century sources and do not recognize it as the ancestor of those modern doctrines risk missing the doctrinal continuity.
A second trap concerns the relationship between jure naturae and jus naturale. The two phrases are closely related but not identical in usage. Jure naturae is typically adverbial — it describes the authority by which a rule operates. Jus naturale names the body of natural law itself. Conflating them in historical research can obscure whether a source is making a descriptive claim about a legal system or a normative claim about a specific obligation.
For contract law research specifically, the Dig. 50.17.206 maxim functions as a gateway to the Roman and civilian foundations of implied contract theory. Researchers tracing the intellectual history of quasi-contract doctrines in common law jurisdictions should treat this maxim as a primary node connecting Roman sources to Bracton, to the common lawyers of the 17th century, and ultimately to modern restitution scholarship.
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Historical Dictionary Support
Burrill's Law Dictionary provides the essential entry: the Latin phrase, its translation, and the Digest citation. Burrill treats jure naturae primarily as a vehicle for the Dig. 50.17.206 maxim rather than as an independent doctrinal term, which accurately reflects how the phrase functions in the sources.
What Burrill does not address is the broader jurisprudential tradition the phrase invokes. The natural law framework underlying jure naturae was central to Grotius, Pufendorf, and their reception by English common lawyers. That intellectual architecture is not visible in a single dictionary entry, but researchers should know it underlies the phrase every time they encounter it.
No significant divergence among historical dictionary sources — the term is sufficiently settled in meaning that variation is minimal. The phrase's significance is less definitional than contextual: it matters because of where it appears and what it is being used to justify.
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Jurisdictional Note
The phrase and its associated maxim appear across both common law and civil law traditions. In civil law jurisdictions, the Roman law source (Dig. 50.17.206) retains direct textual authority. In common law jurisdictions, the maxim was absorbed into equity and later into modern restitution doctrine rather than cited as freestanding authority.
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Encyclopedia Cross-Reference
Contracts — Definition, Nature, and Sources of Contract Law (The Law Mind Contracts & Commercial Law Encyclopedia): For the relationship between natural law foundations and the development of implied contractual obligations and unjust enrichment.
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