Read it here. I'm just starting it. From the syllabus (which is not a part of the Court's opinion, but is prepared by the Reporter of Decisions, and is usually a good summary):
The Chief Justice delivered the opinion of the Court with respect to Parts I and II–A–1:
Article I, Section 8, of the Constitution specifies that "The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises." The Framers recognized the unique importance of this taxing power—a power which "very clear[ly]" includes the power to impose tariffs. Gibbons v. Ogden, 9 Wheat. 1, 201. And they gave Congress "alone … access to the pockets of the people." The Federalist No. 48, p. 310 (J. Madison). The Framers did not vest any part of the taxing power in the Executive Branch. See Nicol v. Ames, 173 U.S. 509, 515. The Government thus concedes that the President enjoys no inherent authority to impose tariffs during peacetime. It instead relies exclusively on IEEPA to defend the challenged tariffs. It reads the words "regulate" and "importation" to effect a sweeping delegation of Congress's power to set tariff policy—authorizing the President to impose tariffs of unlimited amount and duration, on any product from any country. 50 U.S. C. §1702(a)(1)(B).
The Chief Justice, joined by Justice Gorsuch and Justice Barrett, concluded in Part II–A–2:
The Court has long expressed "reluctan[ce] to read into ambiguous statutory text" extraordinary delegations of Congress's powers. West Virginia v. EPA, 597 U.S. 697, 723 (quoting Utility Air Regulatory Group v. EPA, 573 U.S. 302, 324). In several cases described as involving "major questions," the Court has reasoned that "both separation of powers principles and a practical understanding of legislative intent" suggest Congress would not have delegated "highly consequential power" through ambiguous language. Id., at 723–724. These considerations apply with particular force where, as here, the purported delegation involves the core congressional power of the purse. Congressional practice confirms as much. When Congress has delegated its tariff powers, it has done so in explicit terms and subject to strict limits.
