"As for a President's unofficial acts, there is no immunity. The principles we set out in Clinton v. Jones confirm as much."

"When Paula Jones brought a civil lawsuit against then-President Bill Clinton for acts he allegedly committed prior to his Presidency, we rejected his argument that he enjoyed temporary immunity from the lawsuit while serving as President. Although Presidential immunity is required for official actions to ensure that the President's decisionmaking is not distorted by the threat of future litigation stemming from those actions, that concern does not support immunity for unofficial conduct. The 'justifying purposes' of the immunity we recognized in Fitzgerald, and the one we recognize today, are not that the President must be immune because he is the President; rather, they are to ensure that the President can undertake his constitutionally designated functions effectively, free from undue pressures or distortions. '[I]t [is] the nature of the function performed, not the identity of the actor who perform[s] it, that inform[s] our immunity analysis.' The separation of powers does not bar a prosecution predicated on the President's unofficial acts."

From the majority opinion in Trump v. United States, issued this morning.

Where is the line between official and unofficial in the charges against Trump? The lower courts rushed through the question, which means the issues are not properly developed for the Supreme Court:

Despite the unprecedented nature of this case, and the very significant constitutional questions that it raises, the lower courts rendered their decisions on a highly expedited basis. Because those courts categorically rejected any form of Presidential immunity, they did not analyze the conduct alleged in the indictment to decide which of it should be categorized as official and which unofficial. Neither party has briefed that issue before us (though they discussed it at oral argument in response to questions). And like the underlying immunity question, that categorization raises multiple unprecedented and momentous questions about the powers of the President and the limits of his authority under the Constitution. As we have noted, there is little pertinent precedent on those subjects to guide our review of this case a case that we too are deciding on an expedited basis, less than five months after we granted the Government's request to construe Trump's emergency application for a stay as a petition for certiorari, grant that petition, and answer the consequential immunity question.

The effort to hurry seems to have ended up slowing things down. It's not entirely back to square one, though, because the Court does offer some "guidance":

Certain allegations — such as those involving Trump's discussions with the Acting Attorney General — are readily categorized in light of the nature of the President's official relationship to the office held by that individual. Other allegations — such as those involving Trump's interactions with the Vice President, state officials, and certain private parties, and his comments to the general public — present more difficult questions. Although we identify several considerations pertinent to classifying those allegations and determining whether they are subject to immunity, that analysis ultimately is best left to the lower courts to perform in the first instance.... 

In dividing official from unofficial conduct, courts may not inquire into the President's motives. Such an inquiry would risk exposing even the most obvious instances of official conduct to judicial examination on the mere allegation of improper purpose, thereby intruding on the Article II interests that immunity seeks to protect.... 

Nor may courts deem an action unofficial merely because it allegedly violates a generally applicable law....  

Virtually every President is criticized for insufficiently enforcing some aspect of federal law (such as drug, gun, immigration, or environmental laws). An enterprising prosecutor in a new administration may assert that a previousPresident violated that broad statute. Without immunity, such types of prosecutions of ex-Presidents could quickly become routine. The enfeebling of the Presidency and our Government that would result from such a cycle of factional strife is exactly what the Framers intended to avoid. Ignoring those risks, the dissents are instead content to leave the preservation of our system of separated powers up to the good faith of prosecutors.... 

The President enjoys no immunity for his unofficial acts, and not everything the President does is official. The President is not above the law. But Congress may not criminalize the President's conduct in carrying out the responsibilities of the Executive Branch under the Constitution. And the system of separated powers designed by the Framers has always demanded an energetic, independent Executive. The President therefore may not be prosecuted for exercising his core constitutional powers, and he is entitled, at a minimum, to a presumptive immunity from prosecution for all his official acts. That immunity applies equally to all occupants of the Oval Office, regardless of politics, policy, or party....