Legal Definitions - casus omissus

Casus omissus is a Latin legal term that refers to a situation or circumstance that was not specifically addressed or provided for by an existing statute (law) or contract. It represents a gap or an oversight in the written rule, meaning the law or agreement is silent on a particular issue that arises. When a casus omissus occurs, courts often have to interpret existing laws, refer to established legal principles, or, in some cases, create new legal precedent to resolve the matter.

Here are some examples illustrating a casus omissus:

• New Technology and Old Laws: Imagine a city ordinance from the 1990s that prohibits "motorized vehicles" from operating on public walking trails to ensure safety and preserve the natural environment. The ordinance specifically lists cars, motorcycles, and gasoline-powered scooters. Decades later, electric bicycles and personal mobility devices like electric skateboards become popular. A person is cited for riding an electric skateboard on a public trail. The original ordinance has a casus omissus because the lawmakers at the time did not foresee or explicitly include these new types of electric-powered personal transport. A court would then need to determine if an electric skateboard falls under the general intent of "motorized vehicles" as prohibited by the ordinance, or if it represents a new category requiring legislative amendment or a judicial interpretation.
• Unforeseen Events in Contracts: Consider a detailed contract between a software development company and a client for creating a custom application. The contract specifies deliverables, timelines, payment schedules, and penalties for delays caused by either party or common issues like technical failures. However, it completely omits any provision for what happens if a major, unexpected cyberattack on a shared cloud server (not owned by either party) causes a two-month data loss and system outage, halting development. When such an event occurs, neither party has a clear contractual clause to guide their actions regarding project delays, cost overruns, or potential termination. This unforeseen scenario creates a casus omissus in the contract, requiring the parties to negotiate a new understanding or seek judicial interpretation based on general contract principles like force majeure or impossibility of performance.
• Gaps in Comprehensive Legislation: A state passes a comprehensive environmental protection act, mandating strict regulations on industrial waste disposal into rivers and air emissions. The law meticulously details permissible levels for various pollutants and outlines enforcement mechanisms. However, it overlooks a specific type of emerging pollutant, microplastic particles, which are not categorized under any of the listed "industrial waste" or "air emission" definitions, despite their known environmental harm. If a factory is found to be discharging significant amounts of microplastics, the environmental protection act has a casus omissus regarding this particular pollutant. A regulatory agency or court would then face the challenge of addressing this issue without explicit statutory guidance, potentially by broadly interpreting existing clauses or by prompting the legislature to amend the act to include microplastics.