The following comment comes from a Canadian-qualified lawyer who is currently engaged in relinquishment of US citizenship through an Asian consulate:
I am a US citizen by birth to a US parent abroad, relinquishing based on having accepted employment with a foreign government. Here is a link I used to prepare my application, which may be useful to others with atypical cases. It is information only — please do not take it as legal advice, and seek such independently if required.
The US Citizenship and Immigration Services (USCIS) publishes its “Service Law Books”, including its interpretations of various sections of the Immigration and Nationality Act (INA). The link is:
and the links from 349.1 to 349.10 (plus appendices) provide interpretations of the various expatriation provisions in section 349 INA. These interpretations contain a useful overview/summary of the law as it has developed and been applied over time.