interveners

Intervener is a term for a person or organization that takes part in a dispute, inquiry, or decision-making process to influence its outcome, introduce expertise, or protect an interest. The notion is used across legal, administrative, and social contexts, and can refer to formal participants in litigation or more generally to actors who step into a situation to affect its course.

In civil law, an intervener is someone who petitions to join an ongoing case, typically when they have a concrete and direct interest affected by the result. Courts may recognize two paths: intervention of right, where the intervenor has a legally protected interest and no prejudice results from allowing participation; and permissive intervention, where the court grants leave upon showing that the intervention would aid in resolving the dispute. Interveners may present arguments, offer evidence, and seek relief consistent with their interests, but their role is usually limited to issues related to their stake. Interveners are distinct from amicus curiae, who provide information without a direct stake in the outcome.

In other domains, interveners include neutral facilitators or mediators who help parties resolve a dispute, humanitarian or international actors who intervene to address crises, or professionals who intervene in clinical, educational, or public health contexts to prevent harm or improve outcomes. The common thread is the act of stepping into a process to influence its trajectory rather than remaining a passive observer.