A federal court has blocked the Trump administration’s decision to add a citizenship question to the 2020 census, stating that it constitutes an “egregious” violation of federal law. The ruling deals a serious blow to the administration’s plan to use the 2020 census to attack the financial and political resources of immigrants and communities of color.In a decision released Tuesday, Judge Jesse M. Furman determined that the Trump administration's attempt to add a citizenship question to the 2020 census, “would undermine the proposition—central to the rule of law—that ours is a government of laws, and not of men" and that it violated the Administrative Procedure Act (APA) in many different ways — “a veritable smorgasbord of classic, clear-cut APA violations.” In the end, Judge Furman concluded that if the Trump administration got its way and a citizenship question was put on the census, “hundreds of thousands—if not millions—of people will go uncounted in the census.”In particular, Judge Furman ruled that Commerce Secretary Wilbur Ross’s decision was “arbitrary and capricious” pursuant to the APA, which governs federal agency action. As demonstrated at trial, Secretary Ross decided to add a citizenship question in the early days of the Trump administration and only after did it “set out to find a ‘legal rationale’ to support it”— a reverse engineering process that both directly contravenes the APA and goes against the story that Secretary Ross has told for months. During the course of our litigation, we obtained documents that revealed that Secretary Ross lied to Congress about the origin of the citizenship question, testifying that he added the question because the Department of Justice had requested it in order to better enforce the Voting Rights Act (VRA). However, as litigation revealed, Secretary Ross actually started considering a citizenship question almost 10 months before DOJ made its request, and he had even compelled Commerce Department staff to push DOJ to make the ask in the first place.It’s no wonder that Judge Furman determined that Secretary Ross’s March 2018 memo officially adding the question, his sworn testimony before Congress, and the information he initially provided in our lawsuit was “materially inaccurate.”Judge Furman also determined that “Secretary Ross’s explanations for his decision were unsupported by, or even counter to, the evidence” before him. Namely, Ross ignored a voluminous amount of quantitative evidence showing that a citizenship question would both harm the quality of census data and result in a net differential undercount — meaning that noncitizens and Hispanics would disproportionately be undercounted resulting in states and localities with large immigrant and Hispanic communities losing political power and federal funding for crucial social programs. By ignoring large swaths of evidence showing how harmful a citizenship question would be, and by failing to adequately test a citizenship question before putting it on the census form, “Secretary Ross’s decision [was]neither logical nor rational.”The ruling came in a consolidated set of cases brought on behalf of several immigrants’ rights groups, as well as 18 states, 15 cities and counties, the District of Columbia, and the U.S. Conference of Mayors. In June 2018, the ACLU sued to stop the citizenship question from going forward, and on Nov. 5, we commenced a two-week trial before Judge Furman.The Constitution requires that the federal government conduct a census every 10 years to count the total number of all “persons” living in the United States. Everyone is counted without exception — adults and children, citizens and non-citizens alike. The Trump administration added the question for the first time in 70 years despite longstanding opposition to the question from the Census Bureau during both Republican and Democratic administrations.Experts agreed that asking about citizenship on a decennial census survey would have an inevitable and predictable consequence: It would drive down participation and skew the accuracy of the count. So did Secretary Ross: When testifying before the Senate, he conceded that by the administration’s own estimate, the question could result in an undercount of an estimated 1 percent of the population — more than 3 million people.Census population data is critically important for two main reasons. For one, it’s used to apportion representation in Congress, draw congressional and state legislative districts, and allocate votes in the Electoral College. It also determines how an estimated $900 billion in funding is allocated for crucial social service programs such as Medicaid, the Children’s Health Insurance Program, Title 1 funding for elementary and secondary schools, and social services block grants. A significant undercount of immigrant communities of color — a near-certainty if a citizenship question is put on the 2020 census form — will dramatically reduce the political power of, and federal funding allocated to, immigrant communities of color for the next 10 years. Secretary Ross’s purported Voting Rights Act rationale has also fallen apart under even basic scrutiny. DOJ has neither requested nor needed a citizenship question on the census to enforce the VRA in the 53-year history of the law. John Gore — a former top-ranking DOJ official who ghostwrote the DOJ letter requesting a citizenship question — testified that the question is not necessary for VRA enforcement, and that he doesn’t even know whether the citizenship data that DOJ will get from a citizenship question is any better than the data on which DOJ currently relies for VRA enforcement, undercutting Secretary Ross’s entire rationale for the question. And former Attorney General Jeff Sessions even forbade DOJ staff from meeting with Census Bureau experts who wanted to share an alternative proposal to give DOJ higher-quality citizenship data at lower cost for VRA enforcement.Secretary Ross’s justification for a citizenship question, as Judge Furman’s decision shows, is a sham — a deception designed to cover up the true motive of reducing the political power of communities whom the Trump administration has targeted since its first days in office. The Trump administration will no doubt appeal the ruling, perhaps all the way to the Supreme Court. But for now, a federal court stands in the way of a citizenship question on the census.