A relative of mine is a Hong Kong resident who married in China several years ago.

In 1995, his wife and two-year-old son came to Hong Kong, the wife on a two-way permit and the son on a one-way permit. The son subsequently obtained a Hong Kong identity card and a BNO passport, but returned to China with his mother when her two-way permit expired. He now remains in the care of his mother, who is waiting for her one-way permit to Hong Kong.

I have heard that there are rules on permanent residency which say that if a person is away from Hong Kong for more than three years, his right of abode and permanent identity card will be cancelled. Do the rules, if they exist, apply in the case I have outlined? If they do, the difficulties they will cause are obvious, especially because my relative is now in detention in China in connection with some unrelated matters.