The jersey had a print with a well-known protest slogan: "Liberate Hong Kong, our era's revolution".
The 27-year-old activist wore it at a demonstration in June. Now he has been sentenced to 14 months in prison for rioting under a new harsh security law.
The democracy activist admitted guilt last week to "actions with riotous intent" and is the first to be sentenced under the region's new, harsh security law called Article 23. It was passed in March and gives the regime extended possibilities to crack down on political discontent and impose harsh penalties for example for treason or riot.
According to court documents, the 27-year-old told the police that he interprets the slogan on the jersey as a call for Hong Kong to again come under British rule. The demonstration in question was held on June 12, a symbolically important day for Hong Kong's largely suppressed democracy movement.
Hong Kong is, since its return from colonial power Britain in 1997, a "special administrative region" in authoritarian China.
