If the Senate Republicans succeed in confirming President Donald Trump's nominee, Amy Coney Barrett, to the court quickly, she would be able to take part in arguments in the case.
Throughout U.S. history, that language has been interpreted to mean that all residents are counted, regardless of whether they entered the country legally.
The Supreme Court announced plans to review President Trump's anti-immigrant apportionment policy on a timeline that could give him a decision on its legality before, in the event of a Trump defeat this November, he is forced to leave office.
In late July, President Trump issued a controversial memo instructing the Secretary of Commerce to exclude undocumented immigrants from the apportionment base following the 2020 Census.
California, Texas and Florida would get fewer seats than expected in the House of Representatives if President Trump's changes are instituted, while Alabama, Minnesota and OH would keep seats they would otherwise have lost, according to an analysis by the Pew Research Center, a non-partisan think tank.
Democratic state attorneys in NY and several other states sued, arguing that Trump's policy violated the law and the Constitution.
The high court also had the option to affirm or vacate the lower court order from a three-judge panel in NY without agreeing to hold arguments.
But the justices said they would hear an appeal in Trump vs NY, giving the administration an opportunity to revive Trump's policy. New York, giving the administration an opportunity to revive the administration's policy.
The American Civil Liberties Union, representing a coalition of immigrant advocacy groups, said Trump's violation of federal law is "not particularly close or complicated". There are no questions on the Census about your immigration status.
It is also not clear what would happen if Trump is defeated for reelection.
Last month, a lower court ruling blocked Trump's push, calling the presidential memo that called for that unprecedented change unlawful.
The district court said that so long as they reside in the country, undocumented immigrants "qualify as "persons in" a "state" who must be counted.
Once states are allocated the districts, the states themselves draw the districts, which will be used first in the 2022 congressional election. Doing so would shift political power away from areas such as Houston and the Rio Grande Valley and toward less Latino, more rural areas of the state.
Update:This article and its title have been updated to reflect the new Census deadline of October 15, 2020.
The Justice Department did not immediately respond to a request for comment.