Not much information provided in the SMCP online, so hard to understand what's really going on, but I note that he was previously prosecuted for not riding "near the kerb", which appears to have been the Highway Code recommendation. In a blog post he indicated that he has been campaigning to change the cycling rules in HK to allow a more sensible way of riding--sounds good to me--but that this is currently (arguably) against the law, which could explain some of what has happened and why he is now being prosecuted. Authority figures (and former ones) may not take kindly to individual protest campaigns...