Definition
In Roman law, decreta (singular: decretum) were judicial sentences or decisions rendered by the emperor in his capacity as supreme judge of the empire. Distinct from general legislative pronouncements, decreta arose from specific cases brought before the emperor for resolution and carried the force of binding legal authority within the Roman legal system. As a form of imperial constitution, decreta functioned alongside rescripta (written responses to legal questions) and edicta (general proclamations) as mechanisms by which the emperor shaped and declared the law.
The term appears in legal literature primarily in two contexts: first, as a descriptor of Roman imperial jurisprudence, relevant to the study of civil law foundations; and second, through the maxim Decreta conciliorum non ligant reges nostros — "The decrees of councils bind not our kings" — a principle of English constitutional significance asserting the independence of the Crown from ecclesiastical council authority.
Common Confusion
Decreta should not be conflated with rescripta or edicta, the other principal forms of Roman imperial constitution. Rescripta were responses to specific petitions or inquiries and did not always carry universal application. Edicta were general edicts issued prospectively to the public. Decreta, by contrast, were rendered in the course of actual judicial proceedings and resolved particular disputes, though they could acquire broader precedential weight. Historical sources sometimes use "decretum" loosely to mean any imperial or ecclesiastical decree, which can obscure these distinctions in research.
Why It Matters in Research
Researchers encounter decreta most often in two distinct contexts, and conflating them produces errors.
The first is Roman and civil law history. When reading treatises on Roman law — including works by Gaius, Ulpian, or later commentators — decreta appears as a technical category of imperial constitution. Understanding its distinction from other imperial pronouncements (rescripta, edicta, mandata) is necessary to accurately interpret statements about how Roman law developed and was transmitted.
The second and more practically significant context for common law researchers is the maxim Decreta conciliorum non ligant reges nostros, cited in Moore's Reports (906) and carried forward in all three source dictionaries here. This maxim surfaced in English legal and constitutional disputes over the relationship between church council authority and royal prerogative. Researchers working in ecclesiastical law, royal prerogative doctrine, or the history of Crown-church relations in England will encounter this principle and should understand its origin: it is not a Roman law maxim but an English common law assertion invoking Roman terminology. The citation to Moore 906 refers to Sir Francis Moore's Cases, a source from the late sixteenth and early seventeenth centuries, situating the maxim in the formative period of English common law's resistance to papal and conciliar jurisdiction.
Corpus researchers should also be alert to the fact that "decretum" and "decreta" appear extensively in canon law sources — the Decretum Gratiani being the foundational text of medieval canon law — where the term carries ecclesiastical rather than Roman imperial meaning. These usages are related etymologically but functionally distinct, and confusion between Roman imperial decreta and canonistic decreta is a persistent hazard in historical legal research.
Historical Dictionary Support
All three source dictionaries — Black's (1st ed.), Black's (2nd ed.), and Rapalje & Lawrence — provide nearly identical entries: a one-sentence definition identifying decreta as judicial sentences of the Roman emperor, followed immediately by the maxim Decreta conciliorum non ligant reges nostros with the Moore citation. The consistency across sources reflects direct derivation from a common lineage rather than independent analysis.
Notably, none of the three sources distinguishes decreta from other forms of imperial constitution, nor do they situate the term within the broader taxonomy of Roman law sources. This is a meaningful gap. Researchers relying solely on these dictionary entries will receive the English constitutional maxim but little useful guidance on Roman law doctrine. For that substance, primary engagement with Roman law treatises or works such as Justinian's Institutes or Digest — and secondary scholarship on imperial constitutions — is necessary.
The fact that the maxim dominates all three entries suggests that for English-trained lawyers, the primary utility of the term was not Roman law scholarship but constitutional argument about ecclesiastical authority.
Jurisdictional Note
Decreta as Roman imperial constitutions is a concept of historical and comparative law, not operative doctrine in any U.S. or English jurisdiction. The maxim Decreta conciliorum non ligant reges nostros, however, has English constitutional relevance and appears in early modern English case law in the context of Crown-church relations. Civil law jurisdictions with Roman law foundations may use "decreto" or cognate terms in modern statutory contexts, but these are distinct from the historical usage addressed here.