Definition
Prohibita (Latin: "prohibited things") refers to acts that are wrongful solely because they have been forbidden by positive law or statute, as distinguished from acts that are inherently or naturally wrong. The term appears most commonly as part of the compound phrase malum prohibitum — an evil or wrong because it is prohibited — and is analytically paired against its counterpart, mala in se (things wrong in themselves).
Standing alone, prohibita functions as a classificatory label in legal reasoning: conduct falling within this category carries no moral stigma independent of the legislative command that forbids it. The wrongfulness is contingent and artificial. Change the law, and the act ceases to be wrong. Examples historically cited include violations of revenue statutes, licensing requirements, technical regulatory offenses, and certain currency or trade restrictions.
Common Confusion
Prohibita is frequently encountered only as the second element of malum prohibitum, and researchers sometimes treat the two as interchangeable. They are not. Prohibita is the noun — the thing prohibited — while malum prohibitum is the evaluative classification (a wrong because prohibited). The distinction matters when reading Latin maxims or civilian-influenced texts, where prohibita may appear in constructions unrelated to the criminal law taxonomy.
The deeper confusion is between the descriptive and normative uses of the classification. Courts sometimes use mala prohibita to mean merely that a statute creates strict liability; other courts use it to make genuine moral distinctions about the character of the offense. These are not the same inquiry, and conflating them has produced inconsistent results in the case law on mens rea.
Why It Matters in Research
The mala prohibita / mala in se distinction drives consequences across multiple legal doctrines, and researchers who track it through historical sources will encounter several traps.
First, the classification is not static. Acts once treated as mere prohibita — possession of certain substances, for instance — have been recharacterized over time as carrying moral weight akin to mala in se, affecting sentencing philosophy, mens rea requirements, and the availability of certain defenses. A historical source that assigns a category to a specific offense may not reflect modern doctrine.
Second, the distinction carries direct doctrinal weight in criminal law research: courts have used it to determine whether a specific-intent requirement applies, whether ignorance of law may serve as a defense (generally unavailable, but the argument arises more naturally for prohibita offenses), and whether a corporation or principal can be held vicariously liable for the acts of an agent. Researchers working on mens rea problems should move immediately from prohibita to the corpus entries on strict liability and vicarious criminal liability.
Third, in equity and contract research, the distinction surfaces in enforceability questions. Courts have sometimes refused to void contracts merely because they incidentally touched on a malum prohibitum rather than a malum in se, reasoning that the absence of inherent moral turpitude diminishes the public policy objection. This line of reasoning appears in older equity treatises and is easily overlooked in purely statutory research.
Fourth, the term itself (prohibita, without the malum prefix) appears most often in Latin maxims and civil law commentary. Researchers using historical digests and abridgments should search under both PROHIBITA and MALUM PROHIBITUM to capture full coverage.
Historical Dictionary Support
Rapalje & Lawrence treat prohibita exclusively through the entry for MALUM PROHIBITUM, which is the standard approach across the major nineteenth-century dictionaries. The entry cross-references Blackstone's Commentaries (1 Bl. Com. 54) and Starkie on Evidence, and draws the core distinction between wrongs that are mala in se — wrong by their own nature, independent of any human enactment — and mala prohibita, wrong only because the law says so.
The Rapalje & Lawrence entry also includes the maxim malus in uno malus in omnibus (bad in one thing, bad in all), noting its similarity to falsus in uno falsus in omnibus, and flagging that both maxims are "most dangerous in their indiscriminate application." This editorial caution is characteristic of Rapalje & Lawrence's approach and is worth noting: the historical dictionaries do not treat the mala prohibita category as a clean, self-executing rule. The classification was acknowledged even in the nineteenth century to be contested at the margins.
What historical dictionaries do not address: the modern expansion of strict liability regulatory offenses has substantially complicated the prohibita category. Blackstone's era contemplated a relatively narrow class of statutory wrongs with no moral content; the twentieth-century administrative and regulatory state created thousands of such offenses, generating a doctrinal literature that the classical sources do not anticipate. Researchers should treat historical dictionary entries on this point as foundational but incomplete.