I’m really not seeing how this changes much. If anything, it’s plausible this confirms at least one set of guidelines and, I think, makes the case against Trump easier.

https://theconversation.com/above-the-law-in-some-cases-supreme-court-gives-trump-and-future-presidents-a-special-exception-that-will-delay-his-prosecution-232907

Writing for the majority, Chief Justice John Roberts rejected Trump’s claim of absolute immunity from criminal prosecution for official acts taken while he was president, as well as the government’s claim that a former president is not “above the law” and can be criminally prosecuted for all actions done while in office.

Instead, the court ruled that some of the crimes that Trump is alleged to have committed are protected by immunity, but others may not be.

the court first determined that a president is absolutely immune for actions taken that are part of his “core” executive functions. These include the powers explicitly given to him in the Constitution, such as the pardon power and the power to remove executive branch officials, which are part of his “exclusive authority” into which neither Congress nor the judicial system may intrude.

For his noncore powers, which include all those not specifically listed in the text of the Constitution, such as the formulation of domestic policy, the court took a more nuanced approach.

The court also ruled in the immunity case that the president enjoys no immunity from criminal prosecution for nonofficial, private conduct.