It's good to hear a fellow Cantonese person here. I take it you're not from Hong Kong though. So let explains the quirk of the judges and other professions in Hong Kong.
It all basically stem from the colonial days. Back then, ANY British subject has the right to work in Hong Kong and make their fortune and takes it back home with them to retire.
Of course, this is a one way traffic. As Hong Kongers wanting to go to any British empire territories would have to jump through large number of hurdles.
Anyway, so here we have it. Because of this quirk. Any British people can work and live in Hong Kong. It also means they can obtain a Hong Kong ID card after 7 years living in Hong Kong. So these people is happy to keep their British passport, AND still participate in FULL all Hong Kong political and social activities as if they were Hong Kongers.
Case in point, Jimmy Lai who's born in China, but has Hong Kong ID card (on the ground of loving there for 7 years). And holds a Canadian passport!
So these foreign judges with foreign passports can participate in all things Hong Kong because they have ID card. Which entitled them to even sit in Hong Kong's court to pass judgement on recent event with a bias view.
Don't get me wrong, it works the other way as well. Like the English police officer I posted here a few months back shouting "you're a disgrace" to one of the law-majers out on the street supporting the rioters.
Yeah I am in Canada. It wasn't until the riot where the blue side start making youtube video explaining the whole judicial structure. I always thought that foreign judge were invited to move to Hong Kong as a citizen (not just getting an HKID), and become a judge locally, even if they have foreign passport, however from the explanation that went on for the past few months, it is like we have outsourced the judges and their loyalty are questionable.