How can you determine that the bribe was for an official act if “… courts cannot examine the President’s actions on subjects within his “conclusive and preclusive” constitutional authority”? In other words, if courts cannot even examine the official action, then what is the bribe even for? A bribe needs to be connected to an action to be considered a bribe at all.
They can reference the action. They just can’t examine the presidents motivation. But they could present evidence like “President X received $500,000 in cash from Mr Y as recorded on this video. Two days later President X pardoned Mr Y’s brother.”