A letter mailed to a U.S. resident as part of a test run of the 2020 Census. (Michelle R. Smith/AP)

A federal judge has ruled against the Trump administration’s addition of a citizenship question to the 2020 Census, marking the first major ruling in a controversy that has pitted states and cities against top administration officials and is likely to come before the U.S. Supreme Court.

Judge Jesse M. Furman of the U.S. District Court for the Southern District of New York ordered the administration Tuesday to stop its plans to add the question to the survey. Calling Commerce Secretary Wilbur Ross’s decision to add the question “arbitrary and capricious,” he blasted Ross for “egregious” violations of the Administrative Procedure Act.

The New York case is the first of three high-profile trials around the country that are challenging the question and is likely to be a road map for the others, legal experts say.

“Today’s ruling will influence them and help them work through the issues,” said Carl Tobias, a professor at the University of Richmond’s School of Law. “This is a comprehensive opinion from a well-respected judge, [and] today’s ruling is going to carry a lot of weight.”

The government will probably appeal Tuesday’s ruling all the way to the Supreme Court. In the interim, other lower courts could weigh in, opening up the possibility that different district courts could rule on the question in ways that conflict with one another and the high court.

Plaintiffs in the New York trial include 18 states and several cities and jurisdictions, along with civil rights groups. The trial addressed two of seven lawsuits that arose from Ross’s March decision to add the question. A trial over the question is underway in California, and another is set to begin Jan. 22 in Maryland.

Opponents of the question say it would reduce response rates in immigrant communities, possibly affecting congressional redistricting and the distribution of federal funding. The government said the question was necessary to enforce the Voting Rights Act.

Both sides have pushed for a speedy process, given the tight deadlines the decennial survey is up against. Most immediately, the forms and other material for the constitutionally mandated survey are scheduled to be printed this summer, leaving little time for the appeals expected.

Because of the time crunch, conflicting scenarios could play out simultaneously, legal experts say. For example, if the Supreme Court were to rule in the government’s favor on New York after the other lower courts ruled against the government, the Supreme Court could order those courts to reconsider their opinions in light of the higher court’s ruling, said Thomas Wolf, counsel with the Democracy Program at the Brennan Center for Justice at the New York University School of Law.

However, he said, “the other cases could proceed to the extent that they contain claims or issues that wouldn’t have been foreclosed by an adverse ruling from the Supreme Court.”

Tobias said he doubted the case could be heard by the high court before the printing deadline, unless it is rushed through.

“The government could ask to leap over the appeals case in all three cases,” he said. “The Supreme Court can move very quickly if it has to, but it doesn’t really like to do that because it doesn’t make for the best decisions.”

It is unclear what will happen if the matter is unresolved before the printing deadline. A Census Bureau spokesman said he could not address hypotheticals.

In his ruling, Furman said Ross had “ignored, and violated” a statute that requires him to collect data through administrative records instead of through direct inquiries for surveys such as the census.

Furman added that Ross had “failed to consider several important aspects of the problem; alternately ignored, cherry-picked, or badly misconstrued the evidence in the record before him; acted irrationally both in light of that evidence and his own stated decisional criteria; and failed to justify significant departures from past policies and practices — a veritable smorgasbord of classic, clear-cut APA violations.”

Ross also failed to follow other laws, including a statute requiring that he notify Congress of the subjects planned for any census at least three years in advance, Furman wrote, adding that the plaintiffs had proved they would be harmed by the question.

“This ruling is a forceful rebuke of the Trump administration’s attempt to weaponize the census for an attack on immigrant communities,” said Dale Ho, director of the Voting Rights Project at the American Civil Liberties Union, which was a plaintiff in the case.

Justice Department spokeswoman Kelly Laco said, “We are disappointed and are still reviewing the ruling.” She added that the government is “legally entitled to include the question on the census.”

The Trump administration had tried several times to stop the case from going forward, notably through requests to the Supreme Court.

Tuesday’s verdict could affect the remaining two trials, in which civil rights groups and others are suing the government for similar violations of the APA. The administration has sought, unsuccessfully, to stop both.

“Judge Furman’s ruling lays out a very clear road map,” Wolf said. “The initial win here is already setting the table for other district courts to rule in a similar way.”

A key question in the lead-up to the trial was where the request for the question had originated. Ross testified before Congress that it came from the Justice Department, but documents released in the case indicated that he had asked the Justice Department to make the request after consulting with White House adviser Stephen K. Bannon and others.

In his ruling, Furman noted that “Defendants’ own documents and expert witness confirm that adding a citizenship question to the census will result in a significant reduction in self-response rates among noncitizen and Hispanic households.”

Democratic lawmakers have railed against the addition of the question, saying that it would make the survey costlier and less accurate. Undercounts would be more likely in Democratic areas where there are large immigrant communities.

The Supreme Court has scheduled a hearing on one aspect of the case. On Feb. 19, the court is to consider whether Ross and others can be compelled to answer questions about their decision to add the citizenship question. The legal issue is whether challengers of that decision must rely on the administrative record offered by the department or whether the motivations of the officials should also be considered.

In October, the Supreme Court intervened to block the deposition of Ross but allowed other depositions and the New York trial to go forward.

Because the administration says time is of the essence, it could ask the Supreme Court to expand its review to consider Furman’s decision. That might necessitate the court delaying the oral arguments scheduled for February.

The administration in its briefs has already told the court that adding the question was unremarkable. “With the exception of 1840, decennial censuses from 1820 to 1880 asked for citizenship or birthplace in some form, and decennial censuses from 1890 through 1950” also included the question, the administration said.

No census since 1950 has included a citizenship question. One exists on the American Community Survey, but the questionnaire goes out to much smaller subsets of the population.

Robert Barnes contributed to this report.