occurs to me that bribing the president is now /always/ legal, since in every case the only way to distinguish gratuity from bribe is via evidence that could never be admissible
I think it's theoretically possible for a president to be prosecuted for obstruction of justice, but basically guaranteed that no case would actually be tryable.
I think they maybe can, but they'd have to really really try hard to force it (e.g. if Biden asks his friend Tom Friedman to burn down the courthouse where Hunter is on trial maybe you get there, but you really have to lean in hard to find examples)
You'd have to have a case where the president for some reason obstructs justice without using the power of his office in any way. Why a president would ever do that is unclear, since using his office both makes the obstruction much more likely to succeed and impossible to prosecute.
And the majority's understanding of what might make something an official act means that simply being president while you do it might make any given action official.