Definition
A legal duty is an obligation imposed by law — whether by statute, common law, constitution, or regulation — requiring a person to act or to refrain from acting in a specified way. Unlike a moral or social obligation, a legal duty is enforceable: its breach carries legal consequences, which may include liability in tort, breach of contract, criminal penalty, or equitable remedy.
Legal duty operates as the correlative of a legal right. Wherever a legal duty exists, some identifiable person or class of persons holds a corresponding right to performance of that duty. This pairing — duty and right as two sides of the same legal relationship — is foundational to how courts analyze claims across virtually every area of substantive law.
Legal duty arises from multiple sources:
1. Common law duty: Imposed by courts through the accumulated body of case law, most prominently in negligence, where the existence of a duty of care is the threshold question before breach, causation, and damages are even reached.
2. Statutory duty: Expressly created by legislation. Violation may give rise to a private right of action, or may serve as evidence of negligence per se depending on jurisdiction and statutory construction.
3. Contractual duty: Arising from the terms of a valid agreement. The duty runs between the parties to the contract and is defined by their agreement, subject to applicable law.
4. Constitutional duty: Obligations placed on government actors by constitutional provisions. These operate differently from private-law duties and are primarily enforceable through civil rights frameworks.
5. Fiduciary duty: A heightened duty of loyalty and care arising from a relationship of trust and confidence — as between trustee and beneficiary, attorney and client, or corporate officer and shareholder.
Common Language
Wiktionary: "A duty prescribed by the law, to act or forbear from acting."
The ordinary meaning here tracks the legal meaning closely enough that no dramatic gap exists — but the legal term carries structural weight that the plain definition obscures. In everyday use, "duty" suggests moral obligation. In law, "legal duty" is a technical term of art: it must be specifically imposed by a recognized legal source, it must run to a determinate person or class, and its breach must be cognizable in a legal proceeding. The moral resonance of the word can mislead researchers into assuming a duty exists wherever conduct seems blameworthy. Courts regularly hold that no legal duty arose even when harm was foreseeable and the defendant acted badly.
Core Elements
For a legal duty to be actionable, courts generally require:
1. A recognized source of obligation — statute, common law rule, contract, or other legally cognizable basis. Ethical expectations alone do not create enforceable legal duties.
2. A determinate obligor — the party bound by the duty must be identifiable.
3. A determinate obligee — the duty must run to a specific person, defined class, or the public at large in a way that creates corresponding rights.
4. A specific content — the duty must be definable in terms of required or prohibited conduct, not merely aspirational.
The absence of any element is typically fatal to a claim based on breach of that duty.
Why It Matters in Research
Legal duty is the structural hinge of enormous portions of the Law Mind corpus. It appears differently depending on the field:
In tort law, duty is the gatekeeper question in negligence analysis. Historical sources tend to treat duty as a relatively narrow category tied to established relationships (landowner/invitee, physician/patient, carrier/passenger). Modern case law has substantially expanded the concept through foreseeability analysis, but historical dictionaries and treatises will not reflect this expansion. Researchers tracing the development of negligence doctrine should not assume a historical source's silence on a particular duty means courts then would have recognized it.
In contract law, duty interacts with consideration doctrine and the rule against pre-existing duty. A promise to perform an already-existing legal duty is generally not valid consideration — a rule that historical sources address under consideration doctrine rather than under "legal duty" as a heading. Researchers should cross-reference consideration entries when investigating this problem.
In insurance law, the duty to defend and duty to indemnify are distinct obligations with different triggers and different consequences for breach. The distinction matters enormously in research because many historical sources treat them as interchangeable or collapse them under a single heading.
Non-delegable duties — where the law prevents an obligor from escaping responsibility by delegating performance to another — represent a significant area of development largely absent from older dictionary sources. Researchers working in agency, employment, or contractor liability should check encyclopedia sources directly.
The correlative structure (duty/right) appears consistently in analytical jurisprudence sources, particularly in works following Hohfeld's analysis of jural relations, though Hohfeld himself is not within the Law Mind historical dictionary corpus. When historical sources describe legal duty as "correlative to a right," they are invoking this analytical tradition.
Historical Dictionary Support
Bouvier's Law Dictionary defines legal duty as "that which the law requires to be done or forborne to a determinate person, or to the public at large, and is correlative to a right vested in such determinate person." This definition captures the essential structure — the obligatory act or forbearance, the determinate beneficiary, and the correlative right — with admirable economy.
What Bouvier's does not address is the question of how courts determine whether a legal duty exists in novel circumstances. The definition assumes the duty is already established; it provides no analytical apparatus for the threshold question of duty-creation that dominates modern tort law. Researchers using Bouvier's to investigate negligence duty questions will find the definition descriptively accurate but analytically incomplete for modern purposes.
Bouvier's also does not distinguish among the different sources of legal duty — common law, statute, contract, constitutional provision — treating the concept as relatively unified. Modern legal analysis treats these categories as meaningfully distinct, with different standards for recognition and different consequences for breach.
Jurisdictional Note
The elements required to establish the existence of a legal duty in negligence vary meaningfully by jurisdiction. Some states use a relationship-based approach that limits duty to recognized categories; others apply broad foreseeability tests that extend duty more freely. This divergence is most significant in premises liability, bystander liability, and cases involving omissions rather than affirmative acts.
Encyclopedia Cross-Reference
Contracts — Duty to Defend and Duty to Indemnify (The Law Mind Contracts & Commercial Law Encyclopedia)
Delegation of Duties — General Principles and Non-Delegable Duties (The Law Mind Contracts & Commercial Law Encyclopedia)
Contracts — Consideration (Bargained-For Exchange, Legal Detriment) (The Law Mind Contracts & Commercial Law Encyclopedia)