For anyone familiar with the ABC of diplomacy, a diplomat's job is to promote bilateral relations while respecting the laws where they serve.

That's apparently not what Gregory May is doing as US consul general to Hong Kong and Macao. In an online forum in January, May groundlessly blamed the National People's Congress Standing Committee for its explanation of the national security law in the Hong Kong Special Administrative Region and said it weakened its “judicial independence”.

By uttering such words, May was intervening in China's domestic affairs, exceeding his role. That such words are lies further undermines his nation’s relationship with China, a bad reflection on his performance.

To intervene in China's domestic affairs in the HKSAR seems to be a tradition of US diplomats. During the social unrest that almost ruined the city in 2019, US diplomats were seen meeting riot organizers in a hotel, highly possibly "teaching" the latter. In the so-called "Summit for Democracy" in December 2021, US politicians invited Nathan Law Kwun-chung, who is wanted for alleged crimes during the riot. Now it's May's turn to utter rather inappropriate words.

Which is why the Office of Commissioner of the Foreign Ministry to the Hong Kong SAR drew three red lines for the US envoy on Thursday. According to reports, the three red lines are "not to endanger China's national security, not to engage in political infiltration in Hong Kong, and not to slander or damage Hong Kong’s development prospects".

Good diplomats serve bilateral relations instead of being unwelcome persons. No diplomat, regardless of where they come from, should ever be allowed to become a source of chaos in Hong Kong.