Borrowed Robes: Comparative Insights on Sua Sponte Authority and Affirmative Defenses

Affirmative defenses are usually the responsibility of litigants; however, U.S. courts increasingly address them sua sponte under the “Gorilla Rule,” stepping in when issues are so obvious that they are overlooked. If unchecked, such interventions risk turning judges into de facto lawmakers, moving away from their neutral role, while appellate guidance offers mixed signals that can leave lower courts uncertain. Lessons from continental civil-law systems, where proactive judicial involvement is common but carefully limited, show a clear way forward: courts can fill procedural and substantive gaps decisively without overstepping their bounds.