meet the following:

1) the citizen has unequivocally admitted in writing an intent to lose US citizenship

2) the renunciation was made at a US diplomatic office outside the US before a US diplomatic officer

3) and that it must be made voluntarily

The question is who is to determine whether these 3 criteria are meet. The case law Carter V Rubin finding is: "it is the Government which decides for the people, not the individual who decides for himself, when a person is in fact a citizen of the US". The bottom line is, if the US government decides you are a citizen of the US, then you are, regardless what you have done.