P imported barium dioxide. The collector of customs assessed the duty at the rate of six cents per pound. This duty fixed by statute was four cents per pound. The rate was raised by a proclamation of the President. The President issued the proclamation by authority of, § 315 of Title III of the Tariff Act of September 21, 1922, ch. 356, 42 Stat. 858, 941, which is the so-called flexible tariff provision. With the Tariff Commission’s advice and in accordance with specific guidelines, the President could adjust the rates on the tariffs. By that procedure, the President increased the tariff on barium dioxide from 4 to 6 cents per pound. P objected and took suit claiming the entire process was unconstitutional. The case came for a hearing before the Customs Court which held the Act constitutional. P appealed to the United States Court of Customs Appeals. The Attorney General certified that in his opinion the case was of such importance as to render expedient its review by the Supreme Court. The judgment of the United States Customs Court was affirmed. The Supreme Court granted certiorari. The contention of Ps in part is that section 315 is invalid in that it is a delegation to the President of the legislative power, which by Article I, § 1 of the Constitution, is vested in Congress, the power being that declared in § 8 of Article I, that the Congress shall have power to lay and collect taxes, duties, imposts, and excises.