The Hong Kong Court of Final Appeal issued a unanimous judgment Thursday holding that people cannot be convicted of rioting or illegal assembly if they are physically absent from the scene.

The appeal centered on whether the city can prosecute rioting and illegal assembly crimes under the common law doctrine of joint enterprise. Examining sections 18 and 19 of Hong Kong’s Public Order Ordinance, the court found “taking part” to be a necessary element of the crimes.

The judgment stated that “[joint enterprise] cannot be relied upon to fix liability as a principal offender on a defendant who was not present and not acting as part of an assembly together with others so assembled, as required by the two sections.”

However, the new limitation is narrow. The court noted that the “inapplicability of the basic joint enterprise doctrine does not leave any gap” as people can still be convicted under other inchoate offenses including conspiracy. 

The decision comes less than two weeks after a Hong Kong district court convicted a popular activist under China’s controversial security law. The activist, Ma Chun-man, is the second person to be convicted under the law, although it has enabled over a hundred arrests since its enactment in June of 2020.

Nevertheless, lawyers and officials within the city have described the ruling as a landmark decision amidst an increasingly tense relationship with Beijing.