> But having returned to the USA there is no longer any immunity. An extradition could proceed.
They are claiming that for political reasons. That way it is up to the US to refuse extradition, which they obviously and predictably have, and be the 'bad guys'.
The reality is that both governments knew full well from the start that nothing would happen to her the instant she left the UK. The reality is not popular with British public opinion so they are posturing.
There are lots of US bases outside London that conduct US intelligence gathering - e.g RAF Menwith Hill.
For a diplomatic cover, usually something for missions in unfriendly and hostile states, (shades of Cold War le Carré here) it would be for staff at the embassy -- which is in London. So the airbase would have to be considered a branch or part of the London embassy under the Vienna Convention. Yet Menwith Hill and Croughton etc are supposedly RAF bases militarily shared under NATO deals.
Hence all the controversy currently coming out of the woodwork, and numerous articles quoting QCs and ministers disputing the validity at all, or considering it abuse of Vienna, including the exploration piece I linked above. IANAL. :)
But having returned to the USA there is no longer any immunity. A crime is still there to be investigated and prosecuted, an extradition could proceed.
Additionally US-UK extradition agreements both under Thatcher and later under Blair have been notable for their imbalance, but that seems rather academic here.
A balanced discussion of the issues underlying: https://www.diplomacy.edu/blog/sacoolas-affair-diplomatic-im...