Definition
An obsolete writ directed to the sheriff commanding the levy of expenses owed to every citizen and burgess summoned to parliament. The writ operated as a mechanism for compelling reimbursement of the costs incurred by parliamentary representatives in attending and returning from parliament — an obligation that historically fell on the constituency rather than the crown or central treasury.
Why It Matters in Research
Sium is a term a researcher will encounter almost exclusively in historical English sources dealing with early parliamentary procedure and the fiscal obligations of boroughs and constituencies toward their representatives. It has no modern legal application and no surviving procedural equivalent in contemporary law.
The critical navigational point: if this term surfaces in a document, the document almost certainly predates the consolidation of parliamentary practice in the seventeenth century. Coke's citation to 4 Institutes places sium within his systematic treatment of parliamentary jurisdiction and writs, which means researchers working in that text or contemporaneous sources should treat the writ as part of the broader administrative machinery connecting local constituencies to Westminster — not as a general debt-recovery mechanism.
Researchers should also note that the writ sits within a cluster of archaic parliamentary writs (alongside venire facias, the knight's wages writs, and related instruments) that concern the financial relationship between burgesses and the boroughs they represented. Conflating sium with general revenue or taxation writs would be an error; its function is narrow and representative in character.
Because the term appears in no modern statutory or common law context, encountering it in a legal research database almost certainly signals that the underlying source is an early modern or medieval English authority. Treat it as a dating and context marker as much as a legal term.
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) provides the only substantive dictionary entry for this term, drawing directly on Coke's Institutes. The definition is spare: a writ to the sheriff to levy the expenses of citizens and burgesses of parliament. Black's adds nothing beyond the citation to 4 Inst. 46, and no subsequent editions of major legal dictionaries substantially expand on the entry.
The sparseness of the historical record is itself informative. Sium is not a term that generated litigation, commentary, or doctrinal development. It appears to have been a ministerial writ of limited dispute, falling into disuse as the system of paying parliamentary representatives from local funds gave way to other arrangements. Historical sources beyond Coke are effectively silent on the writ's procedural details, which means the researcher has limited secondary material to work from and must rely on Coke's primary text for any depth.