Definition
Latin: "by the authority of Parliament." A formal style used in English legal process during the Interregnum period (1649–1653), when writs and all judicial instruments were issued in the name of Parliament rather than in the name of a sovereign. Following the execution of Charles I in January 1649 and the abolition of the monarchy, the traditional royal styling of writs — which had invoked the authority of the king — was replaced by this parliamentary formula. The style remained in use until Oliver Cromwell was declared Lord Protector in December 1653, at which point process began to issue in his name.
The phrase signals a discrete and constitutionally anomalous episode: a period in which English law operated without a crown, and courts and writs had to be grounded in a different source of sovereign authority.
---
Common Confusion
AUCTORITATE PARLIAMENTI is sometimes loosely grouped with other Latin writ-style formulas as though it were part of the ordinary rotation of English legal forms. It was not. It was a product of emergency constitutional circumstances — the literal absence of a monarch — and has no equivalent in ordinary common law practice before or after the Interregnum. Researchers should not treat it as a variant of standard royal-style process.
---
Why It Matters in Research
This term matters almost exclusively in one context: identifying and dating English legal records from the Interregnum. Any writ, judgment, or court process styled *auctoritate parliamenti* falls within a narrow window — between the execution of Charles I (January 30, 1649) and Cromwell's assumption of the Protectorate (December 16, 1653). The formula thus functions as an internal date marker for archival researchers working with seventeenth-century English legal records.
Be alert to the following traps:
**Dating precision.** The phrase does not cover the entire Interregnum. After Cromwell became Protector, process shifted again. Records from 1653 onward will not carry this formula even if they predate the Restoration.
**Legitimacy questions in contemporaneous sources.** Some courts and practitioners during the period were reluctant participants in the new forms, and there was active legal debate about whether process styled this way was valid — particularly for actions that had been commenced under the old royal style. Researchers reading contemporary commentary or case notes should expect to find that legitimacy, not just form, was contested.
**Restoration-era treatment.** After Charles II was restored in 1660, there were questions about the legal standing of proceedings conducted under Interregnum forms. Parliamentary and judicial sources from the Restoration period sometimes addressed the validity of acts and judgments from this era, and the anomalous styling of process was part of that larger controversy.
**Corpus connections.** Researchers working on Parliamentary supremacy, the evolution of royal prerogative, or the constitutional history of writs will encounter this term as a data point in the longer arc from medieval royal authority through the constitutional crises of the seventeenth century to the settlement of 1688–1689.
---
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) provides the essential entry: the phrase was "the style in which writs and all judicial processes were made out during the great revolution, from the execution of King Charles I. till Oliver Cromwell was declared protector." This is accurate and sufficient as far as it goes.
What Black's does not address — and what researchers should supply from other sources — is the contested legal status of process issued under this style, both at the time and retrospectively. Black's treats the formula as a neutral descriptive fact of legal history rather than engaging with the doctrinal controversy it generated. For the deeper constitutional history, sources on the Interregnum courts, the Rump Parliament's legislative activity, and Restoration-era validation statutes will be necessary. Historical legal dictionaries generally treat *auctoritate parliamenti* as a curiosity of form rather than a subject of substantive analysis, which understates its significance as a window into how English law managed — or struggled to manage — a period of radical constitutional rupture.
---
Jurisdictional Note
This term is specific to English legal history and has no equivalent in other common law jurisdictions, which were either not yet established or operating under different frameworks during the Interregnum. It carries no operative legal meaning in any modern jurisdiction.
---