Which legal concept is used to ensure an agency performs its legal duties?

The correct answer, mandamus, refers to a specific legal remedy that compels a public agency or an officer to perform a duty that they are obligated to complete, especially when there is a failure to do so. This remedy is essentially a court order that requires the entity to carry out its legal responsibilities, ensuring compliance with the law.

Mandamus is significant in administrative law because it serves as a check on administrative agencies, ensuring that they do not neglect their statutory duties. For instance, if an agency is required to issue a permit or take some action within a specified timeframe and fails to do so, a mandamus petition can be filed to compel the agency to act.

The other concepts mentioned do not serve the same function. Judicial review allows courts to evaluate the legality of actions taken by administrative agencies but does not compel action. "Opcertation" appears to be an incorrect term and does not relate to administrative law. Amicus curiae refers to a "friend of the court" brief, which offers information or perspective to a case but does not dictate agency action or enforce legal duties. Thus, mandamus is the appropriate concept for compelling an agency to fulfill its legal obligations.