I might not be a Constitutional scholar, but...

[Silent3]

37. Turns out the gist of the court decision on immunity is just what I said it should be

The breakdown of checks and balances that would create an unaccountable Presidency.

At bottom, former President Trump’s stance would collapse our system of separated powers by placing the President beyond the reach of all three Branches. Presidential immunity against federal indictment would mean that, as to the President, the Congress could not legislate, the Executive could not prosecute and the Judiciary could not review. We cannot accept that the office of the Presidency places its former occupants above the law for all time thereafter. Careful evaluation of these concerns leads us to conclude that there is no functional justification for immunizing former Presidents from federal prosecution in general or for immunizing former President Trump from the specific charges in the Indictment. In so holding, we act, “not in derogation of the separation of powers, but to maintain their proper balance.” See Fitzgerald, 457 U.S. at 754.

And gosh, this wouldn't apply to diplomats at all.