The last decision of the Supreme Court term may be its most impactful ... but perhaps not as impactful as some may think. On a 6-3 decision written by Chief Justice John Roberts, the court ruled that the constitutional separation of powers provides presidents with "absolute immunity" from prosecution for official acts in office -- in terms of 'core' constitutional duties. 

As for other official acts, the court rules that presidents should have the preumption of immunity, but that courts could consider that application on a case-by-case basis. However, Roberts warned with significant portent, presidents have no presumption of immunity from unofficial acts in office:

The parties before us do not dispute that a former President can be subject to criminal prosecution for unofficial acts committed while in office. See Tr. of Oral Arg. 28. They also agree that some of the conduct described in the indictment includes actions taken by Trump in his unofficial capacity. See id., at 28–30, 36–37, 124. 

They disagree, however, about whether a former President can be prosecuted for his official actions. Trump contends that just as a President is absolutely immune from civil damages liability for acts within the outer perimeter of his official responsibilities, Fitzgerald, 457 U. S., at 756, he must be absolutely immune from criminal prosecution for such acts. Brief for Petitioner 10. And Trump argues that the bulk of the indictment’s allegations involve conduct in his official capacity as President. See Tr. of Oral Arg. 30–32. Although the Government agrees that some official actions are included in the indictment’s allegations, see id., at 125, it maintains that a former President does not enjoy immunity from criminal prosecution for any actions, regardless of how they are characterized. See Brief for United States 9. 

We conclude that under our constitutional structure of separated powers, the nature of Presidential power requires that a former President have some immunity from criminal prosecution for official acts during his tenure in office. At least with respect to the President’s exercise of his core constitutional powers, this immunity must be absolute. As for his remaining official actions, he is also entitled to immunity. At the current stage of proceedings in this case, however, we need not and do not decide whether that immunity must be absolute, or instead whether a presumptive immunity is sufficient. 

It's reasonable to note that the issues in the prosecutions of Donald Trump do not involve 'core' constitutional duties. To the extent that they involve official acts -- such as in the January 6 riot -- the courts will still have to suss out whether those are covered by presumptive immunity, as well as which acts are official and which are private.

Roberts notes that the courts involved in these prosecutions have yet to address those questions, necessarily because of the unknown validity of the immunity claims:

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. See 601 U. S., at ___. Given all these circumstances, it is particularly incumbent upon us to be mindful of our frequent admonition that “[o]urs is a court of final review and not first view.” Zivotofsky v. Clinton, 566 U. S. 189, 201 (2012) (internal quotation marks omitted).

Roberts attempts to set up some guidelines for lower courts, again a necessity springing from the novelty of this ruling. Special counsel Jack Smith can't be too happy with the parameters drawn by the majority:

But the breadth of the President’s “discretionary responsibilities” under the Constitution and laws of the United States “in a broad variety of areas, many of them highly sensitive,” frequently makes it “difficult to determine which of [his] innumerable ‘functions’ encompassed a particular action.” Id., at 756. And some Presidential conduct—for example, speaking to and on behalf of the American people, see Trump v. Hawaii, 585 U. S. 667, 701 (2018)—certainly can qualify as official even when not obviously connected to a particular constitutional or statutory provision. For those reasons, the immunity we have recognized extends to the “outer perimeter” of the President’s official responsibilities, covering actions so long as they are “not manifestly or palpably beyond [his] authority.” Blassingame v. Trump, 87 F. 4th 1, 13 (CADC 2023) (internal quotation marks omitted); see Fitzgerald, 457 U. S., at 755–756 (noting that we have “refused to draw functional lines finer than history and reason would support”). 

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. 

Roberts has already cut off a couple of arguments from Smith. The indictment alleged that Trump used the Department of Justice to perform a "sham" election-fraud probe in an effort to overturn the election. However, the DoJ falls entirely within the president's constitutional authority, and so ...

The indictment’s allegations that the requested investigations were “sham[s]” or proposed for an improper purpose do not divest the President of exclusive authority over the investigative and prosecutorial functions of the Justice Department and its officials. App. 186–187, Indictment ¶10(c). And the President cannot be prosecuted for conduct within his exclusive constitutional authority. Trump is therefore absolutely immune from prosecution for the alleged conduct involving his discussions with Justice Department officials. 

Similarly, Roberts writes that the allegations of attempting to corrupt the process used by Mike Pence in his role as President of the Senate could involve presidential immunity. Roberts doesn't flat-out negate that part of the indictment, given that Pence operated in that function as part of the legislative branch, but directed the lower courts to carefully conside the VP's normal role as a member of the executive branch.

However, Roberts makes a point of noting where presumptive immunity ends in this particular case:

Unlike the allegations describing Trump’s communications with the Justice Department and the Vice President, these remaining allegations involve Trump’s interactions with persons outside the Executive Branch: state officials, private parties, and the general public. Many of the remaining allegations, for instance, cover at great length events arising out of communications that Trump and his co-conspirators initiated with state legislators and election officials in Arizona, Georgia, Michigan, Pennsylvania, and Wisconsin regarding those States’ certification of electors. See App. 192–207, Indictment ¶¶13– 52. ...

Unlike Trump’s alleged interactions with the Justice Department, this alleged conduct cannot be neatly categorized as falling within a particular Presidential function. The necessary analysis is instead fact specific, requiring assessment of numerous alleged interactions with a wide variety of state officials and private persons. And the parties’ brief comments at oral argument indicate that they starkly disagree on the characterization of these allegations. The concerns we noted at the outset—the expedition of this case, the lack of factual analysis by the lower courts, and the absence of pertinent briefing by the parties—thus become more prominent. We accordingly remand to the District Court to determine in the first instance—with the benefit of briefing we lack—whether Trump’s conduct in this area qualifies as official or unofficial.

This is where Trump may well have won very little. In an analysis posted before the release of the ruling, Andrew McCarthy predicted a narrow interpretation of presidential immunity, and predicted it would have only enough impact to focus Smith on the more easily tried aspects of the DC case:

I expect that the Court will recognize that presidents have immunity from criminal prosecution for acts that are within the ambit of their executive authority. Ironically, this will be a favor to Biden Justice Department special counsel Jack Smith: It will leave him with a narrow but apparently strong case, based on the so-called fake-electors scheme, that could be tried in the late summer. ...

Smith’s 45-page indictment, if it were kept intact, could take eight weeks or more to try. Depending on how the Supreme Court rules on immunity, and whether it remands immunity issues back to Judge Chutkan for additional factfinding, keeping the case as intact as possible would mire Smith in more immunity litigation and potentially more pretrial appeals. There would be no chance of getting the case to trial prior to Election Day, which is Smith’s goal. (To repeat, I believe that is not just an unseemly goal, it also violates Justice Department rules. But this column is not about my feelings; it is about the likelihood of Smith forcing a trial of Trump prior to Election Day.)

By contrast, a trial of the fake electors scheme would probably take only two or three weeks once a jury was selected. And assuming the Supreme Court holds the Trump defense to its concession during oral argument that the fake-electors scheme did not involve official acts of the presidency, a prosecution centered on that scheme would not bog the case down in additional pretrial litigation and appeals.

Don't be too sure. By insisting that the circuit court hold evidentiary hearings on which acts might be covered under 'presumptive immunity,' those rulings all but guarantee appeals in the pretrial period. This lengthens the ramp-up considerably, a point raised by Amy Coney Barrett in her narrow dissent to Roberts' decision to send all of the issues back to the lower court. She objected to the order that prevents the lower court from proceeding to trial without such an evidentiary hearing, arguing that the trial court could in effect make those decisions as part of a normal evidentiary process. 

The dissents are precisely as one would imagine them to be; Roberts describes them as "a tone of chilling doom that is wholly disproportionate to what the Court actually does today"[.] Just as with the Jarkesy decision and the rejection of the Chevron doctrine in Loper Bright, they paint a picture of a dystopian landscape, in this case where presidents are above the law. The one remaining point of interest, though, comes in the concurrence from Justice Clarence Thomas, who basically briefed the Florida court and Judge Aileen Cannon on the legality of Jack Smith's appointment as special counsel:

In this case, the Attorney General purported to appoint a private citizen as Special Counsel to prosecute a former President on behalf of the United States. But, I am not sure that any office for the Special Counsel has been “established by Law,” as the Constitution requires. Art. II, §2, cl. 2. By requiring that Congress create federal offices “by Law,” the Constitution imposes an important check against the President—he cannot create offices at his pleasure. If there is no law establishing the office that the Special Counsel occupies, then he cannot proceed with this prosecution. A private citizen cannot criminally prosecute anyone, let alone a former President.

No former President has faced criminal prosecution for his acts while in office in the more than 200 years since the founding of our country. And, that is so despite numerous past Presidents taking actions that many would argue constitute crimes. If this unprecedented prosecution is to proceed, it must be conducted by someone duly authorized to do so by the American people. The lower courts should thus answer these essential questions concerning the Special Counsel’s appointment before proceeding. 

Want to bet that Cannon references this concurrence in her upcoming decision on precisely this challenge in the Florida case? Stand by for even more meltdowns in the media and among Democrats. Garland could reassign this to a US Attorney to solve this defect, of course -- but that would mean getting his fingerprints back onto unprecedented prosecutions of a former president. 

I'll have more on the other notable decision today, Corner Post, which will likely fly under the radar. 

Addendum: I would like to express my appreciation, as always, to SCOTUSBlog and to Amy Howe for all of their work in providing the decisions and informed analysis.