Say a president builds up an "official" retirement fund for himself (and friends) by holding a "pardon auction" with top bidding few dozen criminals being released each year during a presidential term. Is this an "official" action covered by this immunity ruling? Their justification could be it keeps taxes lower, etc.
No, the bribery would not be an official act, see footnote 3 of the opinion:
> in a bribery prosecution, for instance, excluding “any mention” of the official act associated with the bribe “would hamstring the prosecution.” Post, at 6 (opinion concurring in part); cf. post, at 25–27 (opinion of SOTOMAYOR, J.). But of course the prosecutor may point to the public record to show the fact that the President performed the official act. And the prosecutor may admit evidence of what the President allegedly demanded, received, accepted, or agreed to receive or accept in return for being influenced in the performance of the act. See 18 U. S. C. §201(b)(2). What the prosecutor may not do, however, is admit testimony or private records of the President or his advisers probing the official act itself. Allowing that sort of evidence would invite the jury to inspect the President’s motivations for his official actions and to second-guess their propriety
Admittedly it’s a bit contradictory, but still helpful I think. The pardon is the official act, and the president is immune from criminal prosecution (and legislation) of the form “it was a crime to give that pardon” without further qualification. The prosecutor cannot compel presidential records or testimony. All the other tools are still available to the prosecutor and the unofficial act of accepting a bribe is still a crime.