Definition
Latin: "between parties." A proceeding, instrument, or legal act that involves two or more parties, each having notice and an opportunity to participate. The phrase carries two distinct applications in legal usage:
1. Instruments and conveyances: A deed or document executed inter partes is one formally made between named parties — "between A, of the one part, and B, of the other part" — as distinguished from a deed-poll, which is executed by one party only. The operative language signals a bilateral or multilateral arrangement in which each party undertakes obligations or makes conveyances to the other.
2. Proceedings: An inter partes proceeding is one conducted with all affected parties present and heard, as opposed to an ex parte proceeding in which only one side appears. In modern administrative and patent law, "inter partes" designates specific adversarial review mechanisms in which a challenging party contests the validity of a right — most prominently in patent practice (inter partes review before the USPTO).
Common Confusion
INTER PARTES vs. EX PARTE: These are direct opposites. An ex parte proceeding involves only one party, often without notice to the opposing side. An inter partes proceeding requires all parties to be present or at least notified. Researchers encountering one term in historical sources should not assume the other's procedural protections apply. Emergency restraining orders and certain injunctions are classic ex parte acts; contested hearings and most trials are inter partes. Confusion between the two in historical pleading records can indicate whether a party had any opportunity to be heard.
INTER PARTES vs. IN PERSONAM: These are not synonymous, though both contemplate parties. In personam describes the reach of a court's jurisdiction over a person; inter partes describes the bilateral or multilateral character of a document or proceeding. A proceeding can be in personam without being inter partes (e.g., a default judgment entered after proper service but without the defendant's participation).
Why It Matters in Research
The phrase does different work in different eras and practice areas, and researchers must track which sense is operative in any given source.
In historical conveyancing records, inter partes is largely a formal term of art identifying the deed as an indenture rather than a deed-poll. Older deeds often open with the explicit recital that the instrument is "made inter partes" — between named grantor and grantee — and this language carries legal weight: obligations and covenants run between the parties, and third-party enforcement questions turn on whether a stranger to the deed can invoke its terms. When researching title chains or early equity disputes about covenant enforcement, the inter partes / deed-poll distinction matters substantively, not just as boilerplate.
In modern administrative and intellectual property research, the term has acquired a highly specific procedural meaning through statute and USPTO rulemaking. Inter partes reexamination (available before the America Invents Act of 2011) and inter partes review (created by the AIA, effective 2012) are distinct proceedings with different estoppel rules, standing requirements, and appeal paths. Researchers using post-2012 patent materials must be careful not to conflate the two; decisions rendered under the old reexamination regime do not govern the new review process.
In civil procedure and family law, inter partes functions as a descriptive label that signals due process protections: a hearing is inter partes when the opposing party was served, appeared, or had the opportunity to appear. This matters when evaluating the preclusive effect of earlier proceedings — a judgment entered without the opposing party having appeared may not carry the same res judicata weight as a fully contested inter partes determination.
Corpus researchers will find the term appearing in pleadings, equity records, conveyancing forms, patent prosecution files, and administrative decisions — often without elaboration, because the term was assumed to be self-explanatory. Context is essential to determining which of its applications governs.
Historical Dictionary Support
The three source dictionaries agree on the core meaning — "between parties" — but each captures a different emphasis. Black's (both editions) leads with the conveyancing sense, illustrating with the category of "papers inter partes" and noting that two persons unite in making mutual conveyances or engagements. The second edition adds a case citation (Smith v. Emery) that grounds the usage in reported law. Burrill goes furthest in explaining the deed-drafting mechanics: the classic indenture formula identifying each party by their "part," with the deed described as made between named persons. Burrill also gestures at the contrast with deeds that are not inter partes — a distinction that later treatises would elaborate as the deed-poll comparison.
What the historical dictionaries collectively miss is the procedural dimension that "inter partes" has acquired in modern administrative and patent law. None of the source entries address proceedings in an adversarial or adjudicative sense; that usage developed substantially after these editions were compiled. Researchers relying solely on these historical entries would underestimate the term's modern reach.
Jurisdictional Note
In U.S. patent law, inter partes review is a federal administrative proceeding before the Patent Trial and Appeal Board governed by statute and USPTO rules, with no direct state-law analog. In civil procedure, the inter partes / ex parte distinction is universal across U.S. jurisdictions, though the specific procedural rules governing ex parte relief (and the showing required to convert such relief to a fully inter partes hearing) vary by jurisdiction and court rules.
Encyclopedia Cross-Reference
The Law Mind Family Law Encyclopedia: Domestic Violence — Emergency / Ex Parte Orders of Protection (family_171) — directly relevant for the inter partes / ex parte contrast in emergency relief proceedings.
The Law Mind Trusts, Estates & Probate Encyclopedia: Revocable Inter Vivos Trusts as Will Substitutes (estates_60) — relevant for understanding instruments operative between parties in the trust and estate context.