The Census Bureau, under the supervision of Commerce Secretary Wilbur Ross, included the question in the 2020 census forms, but in a 277-page court ruling, US District Judge Jesse Furman said Ross did not follow the proper procedures.
"In arriving at his decision as he did, Secretary Ross violated the law," Furman said in his ruling, adding that the Commerce chief "failed to justify significant departures from past policies and practices."
The American Civil Liberties Union, which filed the lawsuit to block the Trump administration's action, welcomed Furman's decision.
"This ruling is a forceful rebuke of the Trump administration’s attempt to weaponize the census for an attack on immigrant communities," Director of the ACLU's Voting Rights Project Dale Ho said in a press release.
In June, the ACLU filed the lawsuit in US District Court for Southern New York state on behalf of a coalition of immigrant-rights groups, claiming that the census question creates a door-to-door federal inquiry of the citizenship status of every member of every household in the United States.
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The US Constitution requires a census every 10 years to count every person in the United States, including citizens and non-citizens.
The census is used to allocate funding for various federal programs and to apportion representation in Congress, the Electoral College, and within state legislatures.
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