Ah - Schumer - another scam, false narrative. That isn’t what they ruled at all. The ruling was actually quite minimalist in its approach. They did not even make a specific ruling as to Trump - they simply declared the immunity exists, and sent it back to the lower courts for them have hearings on whether or not Trump’s actions were official or unofficial and whether or not the immunity applies to any specific actions.
:: and sent it back to the lower courts ::
This is where Chucky is foiled...again.
Often, SCOTUS will send such things back to Congress to Re-write things to make them Constitutional.
No such language this time..
It is entirely within the Third Branch; the Courts only.