It's a little amusing that Roberts is citing Breyer there, in Clinton v. Jones, that's the Paula Jones case, where Breyer is arguing, in a unanimous decision (Democrat Stevens wrote the opinion), that Clinton was not immune (from civil lawsuits based on private conduct), in spite of the fact that Clinton was indeed the president at the time and the case was certainly "distracting his time and energy", the thing the Framers are said to have been so particularly tender about, and in spite of the fact that this was only the third time in American history that such a suit had been filed against a sitting president. Clinton had failed to prove, Breyer thought, that the US government needed for Clinton to have the immunity:
As Madison pointed out in The Federalist No. 51, "[t]he great security against a gradual concentration of the several powers in the same department consists in giving to those who administer each department the necessary constitutional means and personal motives to resist encroachments of the others. The provision for defense must in this, as in all other cases, be made commensurate to the danger of attack." Id., at 321-322 (emphasis added). I agree with the majority's determination that a constitutional defense must await a more specific showing of need; I do not agree with what I believe to be an understatement of the "danger."
It seems to me that with Trump v. United States the Court has turned this upside down, shifting the burden of proof from the offender to the offended. Henceforth (I once knew a cat called Henceforth, and a pretty good cat too), it will just be assumed that the president shouldn't be asked to answer any questions, even after they've left office, nor should his White House employees, even when they're glorified nursemaids for the cranky old psychopath, like poor Hope Hicks helping him ride his way through the scandal of the Access Hollywood video. She was part of the apparatus enabling Trump's "energetic, vigorous, decisive and speedy execution of the laws" when he was paying his hush money debt to Michael Cohen with $420,000 in checks disguised as legal fees so nobody would know about it, so it looks like her testimony in the New York case should not have been given, and his conviction now seems likely to turn into a mistrial, even though you'd be hard put to name any occasions when he executed any laws at all beyond his photo op bill-signing moments with the presidential Sharpie.
It would be fun to put that on trial, wouldn't it? "Do you recall faithfully executing any laws in 2017, Mr. Trump? Can you list some of those for the jury?" But of course it's unimaginable.
It's also difficult to imagine a Supreme Court majority now citing Federalist 51, with its focus on checks and balances among the three branches, and Madison wistfully letting on how much he wished he could have had the president and Supreme Court justices directly elected: