Definition
Lagu is an Old English term meaning "law." In Anglo-Saxon legal usage, it denoted both the concept of law generally and, more specifically, the territorial district or region within which a particular body of law held force. The term appears most often in compound forms identifying the distinct legal customs of regional populations in pre-Conquest England — most notably Dena lagu (the law of the Danes, or Danelaw), Mercna lagu (the law of the Mercians), and Wes-Seaxna lagu (the law of the West Saxons).
Common Confusion
Lagu should not be confused with lex, the Latin term for law that appears throughout medieval English legal records once Latin became the dominant language of legal drafting after the Conquest. While lagu and lex are functionally equivalent in translation, they signal different historical moments and textual traditions: lagu marks a document or source as Anglo-Saxon in origin or orientation, while lex marks the Latin-language, post-Conquest or ecclesiastical legal tradition. Conflating the two can mislead researchers about the provenance and applicable legal framework of a source.
Why It Matters in Research
Lagu is primarily a term of historical and linguistic significance rather than a term with continuing doctrinal life. Researchers encounter it almost exclusively in Anglo-Saxon source materials, medieval chronicles, and legal histories treating the pre-Conquest period. Its importance lies in understanding how early English law was organized territorially rather than as a unified national system — a structural reality that shaped the development of the common law over centuries.
The compound forms of lagu are the more practically useful research handles. Dena lagu in particular is the root of the modern English word "Danelaw" and connects directly to scholarship on the Scandinavian legal influence in northern and eastern England. Researchers working on the origins of jury trial, land tenure customs, or early criminal procedure in the Danelaw region will encounter lagu as a recurring organizing concept.
A research trap: sources treating lagu in isolation may suggest it means only "law" in the abstract, obscuring its territorial dimension. The territorial sense is often the more consequential one for legal historians, since the regional law-districts denoted by lagu compounds were administratively real and carried distinct procedural and substantive rules.
Lagu also provides a useful conceptual bridge for researchers moving between Anglo-Saxon primary sources and later Norman-era texts that begin consolidating these regional laws. After the Conquest, the plural legal landscapes signaled by lagu compounds gradually gave way to a centralized common law — but the memory of these distinctions persisted in legal argument well into the medieval period.
Historical Dictionary Support
Both editions of Black's Law Dictionary reproduce the same compact entry: lagu means "law" in old English law, and the term was also used to express the territory or district in which a particular law was in force, with Dena lagu and Mercna lagu offered as illustrations. The two editions are in complete agreement, with no substantive variation.
What the historical dictionary entries do not capture is the broader context of Anglo-Saxon legal pluralism that makes lagu significant. The entries treat it as a vocabulary item rather than as a structural concept — useful for identifying the term in a primary source but insufficient for understanding why regional law-districts existed or how they functioned. Researchers should supplement Black's with dedicated Anglo-Saxon legal histories and philological sources for fuller treatment.
Jurisdictional Note
Lagu is specific to pre-Conquest English legal history and has no operative meaning in any modern jurisdiction. Its significance is confined to historical legal research concerning Anglo-Saxon England and the regional legal customs of the Danelaw, Mercia, and Wessex.