What Happens When U.S. Personnel Serve a Foreign Intelligence Agency?

Remember that story about the iPhone hacking tool called Karma? Lawfare published a good piece detailing the consequences of U.S. spies working for a foreign intelligence agency.
Along the way, the Americans came to appreciate that their efforts at times did indeed include surveillance of political opponents of UAE authorities, and further that the UAE service at times targeted Americans despite assurances that this would not occur (or at least that the operations Project Raven in particular conducted or supported would not be directed at Americans).
That’s probably the biggest point of the story. Americans spying on Americans on behalf of another country.