The phrase "was party to" is often used to refer to someone who was involved in something, usually something negative. In order to express the opposite meaning, one could use antonyms such as "unaware of," "innocent bystander," or "not involved." These words suggest that someone had no knowledge or role in an event, and may even imply that they would not have supported it if they had. Using these antonyms can help to communicate a more positive or neutral perspective on a situation, instead of one that casts blame or judgement.