It is trite law that mere presence at the scene of an unlawful assembly or a riot is not unlawful. However, what it takes to shift a person from an innocent bystander to an active participant in the eyes of the law is less well known. In HKSAR v Choy Kin Yue (2022) 25 HKCFAR 360, the Hong Kong Court of Final Appeal accepted that the Respondent who filmed the participants in an unlawful assembly had acted in a provocative manner by his conduct of filming, and further held that the Respondent had intentionally taken part in the unlawful assembly. The Court therefore allowed the prosecution’s appeal and restored the Respondent’s conviction. This case comment argues that the court’s reasoning is problematic in four aspects, and that the case has led to increasingly blurred boundaries between an innocent bystander and an active participant in an unlawful assembly or riot.