A judge or justice (particularly of the US Supreme Court) who rules in accordance with their personal ideology rather than with how the law is strictly written; often used in a derogatory or pejorative sense. Primarily heard in US, South Africa. Many attributed the strict environmental rulings to the activist judge who was appointed last November and is known for his love of nature.

A court justice whose rulings are dictated more by personal leanings than the law. I can't believe that judge! What is he, an activist justice—handing out rulings based on his own bent?