Prosecuting former US citizen for US crimes? (Case in the news in Australia)
There's a case local to me in Australia that made me curious about US citizenship and the question of relinquishment versus renunciation. The case is of Dan Duggan, who is one of these former US military pilots accused of training Chinese fighter pilots in violation of US arms trafficking regulations. He has been in an Australian jail since 2022 [fighting extradition to the United States] (https://www.abc.net.au/news/2026-04-16/former-us-marine-pilot-dan-duggan-to-be-extradited-australia/106570508). Something that confused me in earlier press coverage was that there seemed to be a lack of clarity about when he ceased to be a US citizen. His family's website makes a big deal about sovereignty and him being a sole Aussie citizen since 2012, when the alleged crimes occurred, but some of the media coverage claimed a date of 2016 for his ceasing to be a US citizen. I didn't really understand how there could be confusion about something like that.
I did a bit of digging, and it seems like he didn't renounce his US citizenship (where you go to a consulate and do the oath of renunciation that is effective immediately), but rather relinquished it, filing paperwork in 2016 that set the date of the relinquishment in 2012, when he took his Australian oath of citizenship. Legally, can the relinquishment of citizenship be backdated like that? If a crime were committed after becoming a duel citizen, could relinquishing your citizenship later mean you couldn't be prosecuted by the US? I'm curious about what this looks like from a US legal perspective.
(This might be moot in this case, since according to the article I linked above the pilot training occurred between 2009 and 2012, not just in 2012, but I'm still curious about the answer.)