Trump just sued the IRS (and the Treasury Department) for $10 billion because a (private) contractor thereof leaked Trump's tax returns in the past. But such a lawsuit seems to me the mother of all conflicts of interest from a sitting US president, since he names the current heads of these departments, who'll likely be like "sure boss, let's settle, here's the check, don't fire me".
I'm curious if there is precedent for this kind of lawsuit from a sitting US president against the US, and what were the outcomes.