A federal judge blocked the Trump administration’s plan to put a question about citizenship on the 2020 census, which will help determine U.S. elections, congressional seats and federal funding decisions for a decade.

The ruling comes after a two-week trial in Manhattan that the government sought more than a dozen times to derail. The Supreme Court may have the last word. It’s hearing an appeal related to the trial in February in hopes of handing down a decision before the Census Bureau has to finalize its questionnaire.

“Hundreds of thousands _ if not millions _ of people will go uncounted in the census if the citizenship question is included,” U.S. District Judge Jesse Furman said in a 277-page opinion.

“In arriving at his decision as he did, Secretary (Wilbur) Ross violated the law,” Furman said, adding the secretary “violated the public trust” in doing so with respect to the census.

The Administrative Procedures Act requires an agency to “consider all important aspects of a problem,” study relevant evidence and come to a conclusion supported by it, comply with procedures and laws and explain the facts and reasons for the decision, Furman said. Ross’s decision “fell short on all these fronts,” the judge said.

Furman, who held the trial without a jury, dealt with the first of several lawsuits filed by dozens of states and cities to block the question from the once-a-decade survey, where it hasn’t appeared since 1950. As the first, it will encourage the plaintiffs in the New York case as well as those in similar lawsuits in California and Maryland likely to go to trial early next year, said Margo Anderson, a retired professor of history and urban studies at the University of Wisconsin, who opposes the question.

The ruling ignores both the law and the history of the census, said Hans von Spakovsky, a senior legal fellow at the conservative Heritage Foundation in Washington who manages the group’s Institute for Constitutional Government. Federal law gives the commerce secretary the full authority to determine what questions will be used on the survey, he said, and a citizenship question was first asked in 1820 and is currently included on the annual American Community Survey, which goes to about one out of every 36 households.

“It will also prevent us from getting accurate census data on citizens and noncitizens from across the country _ since the ACS is limited in scope _ which is vital in enforcement of the Voting Rights Act, distribution of federal funds and having an informed debate about immigration policy,” von Spakovsky said.