Every ten years, the Nation undertakes a census. The census plays a critical role in apportioning Members of the House of Representatives among the States, allocating federal funds to the States, providing information for intrastate redistricting, and supplying data for numerous initiatives conducted by governmental entities, businesses, and academic researchers. Congress has given both the Secretary of Commerce and the President functions to perform in the enumeration and apportionment process. The Secretary must “take a decennial census of population . . . in such form and content as he may determine,” and the President in turn must transmit to Congress a “statement showing the whole number of persons in each State, excluding Indians not taxed, as ascertained” under the census. Under 46 Stat. 26, 2 U. S. C. §2a(a) the President must apply a mathematical formula called the “method of equal proportions” to the population counts in order to calculate the number of House seats for each State. D issued a memorandum to the Secretary respecting the apportionment following the 2020 census. It announced a policy of excluding “from the apportionment base aliens who are not in a lawful immigration status.” D ordered the Secretary, in preparing his §141(b) report, “to provide information permitting D, to the extent practicable, to exercise D’s discretion to carry out the policy.” Various States, local governments, organizations, and individuals (Ps) made several challenges to the memorandum. A three-judge District Court held that Ps had standing to proceed in federal court because the memorandum was chilling aliens and their families from responding to the census, thereby degrading the quality of census data used to allocate federal funds and forcing some plaintiffs to divert resources to combat the chilling effect. The District Court held the memorandum violates §141(b) by ordering the Secretary to produce two sets of numbers-a valid tabulation derived from the census, and an invalid tabulation excluding aliens based on administrative records outside the census. It ruled that the exclusion of aliens on the basis of legal status would contravene the requirement in §2a(a) that D states the “whole number of persons in each State” for purposes of apportionment. The District Court declared the memorandum unlawful and enjoined the Secretary from including the information needed to implement the memorandum in his §141(b) report to D. D appealed.