Definition
A writ directing justices not to hold an assize in a particular case. The writ operated as a prohibition or stay, preventing the convening of an assize court for the specific matter to which it applied.
Why It Matters in Research
Sisam is an archaic procedural writ with no modern counterpart. Researchers encountering the term will find it almost exclusively in early English common law sources, particularly materials drawn from the Registrum Omnium Brevium (Register of Original Writs). The term has no continuing life in Anglo-American legal systems and does not appear in American practice. Its significance is antiquarian rather than doctrinal: the writ represents one of the many specialized instruments once used to regulate the jurisdiction and timing of assize proceedings in medieval England. Researchers working on the history of writs, assize procedure, or the development of English courts will need to situate sisam within the broader architecture of original writs — a system where specific writs controlled nearly every step of judicial process. Do not confuse the writ's prohibitory function with the general writ of prohibition; sisam was narrower in scope, directed at preventing an assize specifically rather than staying a court's jurisdiction generally.
Historical Dictionary Support
Black's Law Dictionary provides the sole surviving dictionary definition of any substance: "A writ forbidding the justices from holding an assise in a particular case," with attribution to the Registrum Omnium Brevium at page 221. The entry is spare and offers no further procedural context. No other major historical law dictionaries appear to carry the term, which reflects how thoroughly assize procedure and its supporting writs fell out of use following the English judicature reforms of the nineteenth century. The Registrum Omnium Brevium, the foundational medieval collection of approved writ forms, is the primary source; researchers needing more than Black's single-sentence entry will need to consult that source directly or secondary works on medieval English writ practice such as the scholarship of S.F.C. Milsom or Frederick Pollock and Frederic William Maitland's The History of English Law.
Jurisdictional Note
Sisam is exclusively a historical English common law writ. It has no recognized equivalent in American, Canadian, Australian, or modern English law. Researchers working outside medieval and early modern English legal history will not encounter it in operative sources.