After pushing the U.S. Supreme Court to rule quickly on challenges to President Donald Trump’s plan to exclude undocumented immigrants from the 2020 census apportionment, the government’s lawyer faced questions from the justices on why the administration could not tell them now if and how the plan will be implemented.

The court on Monday heard arguments in the case Trump v. New York. The Trump administration is asking the justices to vacate an injunction barring the secretary of commerce from following Trump’s directive that he receive, with the total population count, information that would allow him to exclude undocumented immigrants to the maximum extent feasible from his calculations for apportionment of U.S. House seats.