President Donald Trump’s main legal authority for his order to exclude undocumented immigrants from the 2020 census apportionment is a 1992 U.S. Supreme Court decision that was argued by then U.S. principal deputy solicitor general John Roberts Jr.

In Trump’s July 21 “Memorandum on Excluding Illegal Aliens From the Apportionment Base Following the 2020 Census,” the president relies on the justices’ ruling in Franklin v. Massachusetts for his argument that he has the discretion to remove those aliens from his final calculation of the number of U.S. Representatives to be apportioned to each state.