>
I'm fairly sure there's a full and complete list of these is explicitly in the Constitution.Roberts disagrees in the decision (p. 17):
> Distinguishing the President’s official actions from his unofficial ones can be difficult. When the President acts pursuant to “constitutional and statutory authority,” he takes official action to perform the functions of his office. Fitzgerald, 457 U. S., at 757. Determining whether an ac- tion is covered by immunity thus begins with assessing the President’s authority to take that action.
> But the breadth of the President’s “discretionary respon- sibilities” 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 pal- pably beyond [his] authority.” Blassingame v. Trump, 87F. 4th 1, 13 (CADC 2023) (internal quotation marks omit- ted); 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 of- ficial conduct to judicial examination on the mere allegation of improper purpose, thereby intruding on the Article II in- terests that immunity seeks to protect. Indeed, “[i]t would seriously cripple the proper and effective administration of public affairs as entrusted to the executive branch of the government” if “[i]n exercising the functions of his office,” the President was “under an apprehension that the motives that control his official conduct may, at any time, become the subject of inquiry.” […]
> Nor may courts deem an action unofficial merely because it allegedly violates a generally applicable law. For in- stance, when Fitzgerald contended that his dismissal vio- lated various congressional statutes and thus rendered his discharge “outside the outer perimeter of [Nixon’s] duties,” we rejected that contention. 457 U. S., at 756. Otherwise, Presidents would be subject to trial on “every allegation that an action was unlawful,” depriving immunity of its intended effect. Ibid.
* https://www.supremecourt.gov/opinions/23pdf/23-939_e2pg.pdf