Definition
Comitatu commisso (Latin: "the county having been committed") is a writ or commission by which a sheriff is formally authorized to enter upon the duties and administrative charges of a county. It is the instrument of appointment or authorization by which the crown or governing authority entrusted the management of a county to a sheriff, effectively commissioning that officer to exercise jurisdiction over the shire. The phrase captures the moment of delegation — the county is "committed" to the sheriff's charge — and the writ gave legal force to that entrustment.
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Common Confusion
Comitatu commisso is easily conflated with the broader concept of posse comitatus, a related Latin term denoting the sheriff's power to summon the able-bodied men of a county to assist in law enforcement. The two concepts are legally distinct: comitatu commisso is the instrument authorizing the sheriff's office itself, while posse comitatus refers to one of the powers that office carries. A researcher encountering either phrase in historical documents should confirm which concept is actually at issue before drawing conclusions about the source's legal context.
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Why It Matters in Research
This term appears almost exclusively in early English legal history and in sources treating the office of the sheriff in its medieval and early modern form. Researchers are unlikely to encounter it in American case law or statutory materials, but it surfaces in treatises on the English common law foundation of county governance and in discussions of how sheriffs derived their authority.
The primary research trap is mistaking this writ as a source of ongoing operative legal authority in any modern context. It is a historical instrument. Its significance today is doctrinal genealogy, not active law. Scholars tracing the roots of American sheriff powers, posse comitatus doctrine, or county-level law enforcement authority will find this term useful as a pointer to how English law structured the delegation of county administration — a structure the American colonies inherited and partially adapted.
The connection to the Posse Comitatus Act (18 U.S.C. § 1385) is indirect but genuine: the Act's very title borrows from the same Latin tradition of county-based law enforcement authority. Understanding comitatu commisso helps frame why "posse comitatus" carried such specific legal weight when Congress chose it as the name for federal legislation restricting military involvement in civilian law enforcement.
Researchers working in Law Mind's historical sources should note that both Black's entries cite "Reg. Orig. 295" (Registrum Omnium Brevium, a register of original writs), which is the appropriate primary source for verifying the form and historical usage of this writ. Secondary citation chains that skip the register and rely solely on Black's should be treated with caution.
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Historical Dictionary Support
Both the primary and supplemental editions of Black's Law Dictionary give identical substantive definitions, varying only in a minor citation styling difference (one renders "Reg. K Orig." and the other "Reg. Orig."). The definitions are brief and functional, establishing only that the writ authorizes a sheriff to enter upon county charges. Neither edition elaborates on the procedural context in which the writ was issued, the form it took, or whether it was distinct from a sheriff's general commission. This brevity is typical of Black's treatment of highly archaic Latin writs: the entries preserve the term for historical reference without attempting doctrinal depth.
Historical legal dictionaries from the English tradition, including Jacob's Law Dictionary and Tomlin's Law Dictionary, provide the broader context for understanding how the sheriff's commission operated within the system of royal writs. Researchers who need more than the Black's stub should consult those sources alongside Bracton and later treatises on the English sheriff's office for a complete picture.
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Jurisdictional Note
Comitatu commisso is an instrument of English common law with no direct American statutory or constitutional analogue. The sheriff's authority in American jurisdictions derives from state constitutional provisions, statutes, and common law inheritance rather than from any surviving writ of this form. Its relevance in American legal research is historical and foundational only.
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Encyclopedia Cross-Reference
Posse Comitatus Act — Restrictions on Domestic Military Operations and Exceptions (The Law Mind Military, Veterans & Admiralty Law Encyclopedia)
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