Definition
A medieval English customs duty levied on imported wine, assessed per tierce — a standard cask of approximately 42 gallons. Modiatio was a fiscal imposition collected at port, functioning as an excise on wine merchants bringing goods into England. It is a term of historical legal significance only; it has no analog in modern tax or customs law.
Why It Matters in Research
Modiatio is principally encountered in records of medieval English port and customs administration, ecclesiastical estate documents, and monastic chronicles — the Monasticon Anglicanum being the primary source Bouvier cites. Researchers working in early English revenue law, trade regulation, or manorial records may encounter the term in Latin-language documents alongside related impositions such as prisage, butlerage, and tunnage. It is not a term that appears in modern statutory or case law.
The chief navigational trap is confusion with other wine-related duties of medieval English law, which operated under distinct legal authorities and collection mechanisms. Tunnage (or tonnage), for instance, was a parliamentary grant levied by the tun rather than the tierce, while prisage was a prerogative right of the Crown to claim a portion of wine cargoes directly. Modiatio was a separate, duty-based charge, though in practice these impositions could overlap in port records and estate accounts.
Researchers should also note that the Latin maxim appended to the Black's entries — Modica circumstantia facti jus mutat ("A small circumstance attending an act may change the law") — is an entirely unrelated legal principle that appears in both editions of Black's immediately following the modiatio entry. This proximity is an artifact of alphabetical arrangement, not conceptual connection. Do not read the maxim as explanatory of modiatio.
Historical Dictionary Support
Black's Law Dictionary (1st and 2nd editions) and Bouvier's Law Dictionary agree on the essential definition: modiatio is a duty paid per tierce of wine in old English law. The entries are nearly identical across all three sources, which reflects the narrow historical usage of the term and its absence from any active legal development.
Bouvier adds the citation to Monasticon Anglicanum, volume II, page 144, the major antiquarian compilation of English monastic records — a useful pointer for researchers pursuing primary source verification. Neither edition of Black's provides a primary source citation, making Bouvier the more useful starting point for documentary research on this term.
None of the three sources provide any English statutory basis, case law, or administrative context beyond the bare definition. The entries collectively function as a gloss rather than a legal analysis, which is consistent with modiatio's status as a defunct historical imposition of limited doctrinal significance.
Jurisdictional Note
Modiatio is exclusively a term of old English law. It has no recognized equivalent in American, Scottish, or continental legal systems and does not appear in modern customs or excise frameworks in any jurisdiction.