(Bloomberg) -- The U.S. Supreme Court put on hold the Trump administration’s plan to include a citizenship question on the 2020 census, prompting President Donald Trump to say he’ll explore trying to delay a survey that by law must be conducted next year.Issuing the final opinion of its term, a divided court said Thursday that Commerce Secretary Wilbur Ross’s stated rationale for including the citizenship question was “contrived” and couldn’t be squared with the evidence about his true motivations. Chief Justice John Roberts joined the court’s liberals in the majority. Trump, who’s in Japan for the Group of 20 summit, tweeted that he’s “asked the lawyers if they can delay the Census, no matter how long.” He said it “seems totally ridiculous that our government, and indeed Country, cannot ask a basic question of Citizenship in a very expensive, detailed and important Census, in this case for 2020.”The court’s decision sets up a race against the clock for the Commerce Department, which houses the Census Bureau, to put forward a justification that can pass legal muster. Any new effort to include the question is sure to face a legal fight that under normal circumstances would take months and land back at the Supreme Court.The U.S. Constitution requires a census every 10 years, and census day is set by federal law as April 1, so it’s unlikely the administration would be able to delay the survey without congressional agreement. The administration has said the 2020 census questionnaire needed to be ready for printing by June 30; those challenging the citizenship question had said it could be finalized as late as Oct. 31. Opponents contend that the citizenship question would reduce participation in the survey and that administration officials hid their true aim of boosting Republican and white voters. Ross said the goal was to help the Justice Department enforce the Voting Rights Act, which protects minority voters.“Altogether, the evidence tells a story that does not match the explanation the secretary gave for his decision,” Roberts wrote for himself and the court’s four liberals, taking a slap at the Trump administration’s decision-making process. He added: “the VRA enforcement rationale -- the sole stated reason -- seems to have been contrived.”The Supreme Court ruled for the administration on other points. A differently configured majority of justices said Ross was justified in rejecting the recommendation of the Census Bureau that the question not be included because it would cut responses by millions of people.Ross “determined that reinstating a citizenship question was worth the risk of a potentially lower response rate,” Roberts wrote for himself and the other four conservative justices. “That decision was reasonable and reasonably explained, particularly in light of the long history of the citizenship question on the census.” ‘Cutting Corners’Opponents of the citizenship question declared victory, saying it will be almost impossible for the administration to complete that process and win a court fight in time.“If they try to do this over the weekend, that is I think a clear sign of cutting corners that does not comport with reasoned decision making,” said American Civil Liberties Union lawyer Dale Ho, who argued the case.New York Attorney General Letitia James said “we’ll see them in court again” if the administration offers a different pretextual explanation.“The question right now is really all about timing,” she said. “The question is whether Mr. Ross will seek out experts and make a decision with respect to this question and decide to go back to the district court.” Ross is also in Japan at the moment.‘Lawful Exercises’ Justice Department spokeswoman Kelly Laco said: “We are disappointed by the Supreme Court’s decision today. The Department of Justice will continue to defend this administration’s lawful exercises of executive power.”The Census Bureau said in a statement, “The decision is currently being reviewed.”The Trump administration has also tangled with House Democrats over its plan to add the citizenship question. The Oversight and Reform Committee, which is investigating officials’ motivation for adding the question, voted to hold Ross and Attorney General William Barr in contempt of Congress earlier this month for withholding documents on the decision. The outcome of the dispute could affect the allocation of federal dollars and congressional districts. California, Texas, Arizona, Florida, New York and Illinois may each be at risk of losing at least one seat in the House of Representatives. No ‘Empty Ritual’ Ross said he added the citizenship question because the Justice Department had said it would help with enforcement of the Voting Rights Act, the landmark 1965 law designed to protect the rights of racial minorities at the polls. But Roberts said U.S. District Judge Jesse Furman in New York was right to call that explanation a pretext. The chief justice pointed to evidence that Ross made his decision long before receiving the Justice Department letter, and that Ross actually solicited the request by speaking with then-Attorney General Jeff Sessions.“If judicial review is to be more than an empty ritual, it must demand something better than the explanation offered for the action taken in this case,” Roberts wrote.Furman said Ross committed a “veritable smorgasbord” of violations of the federal law that governs administrative agencies. That law requires officials to make major decisions through a reasoned process and to give an honest explanation for their actions.The Trump administration said Ross was entitled to rely on the Justice Department’s analysis about the value of citizenship data for Voting Rights act enforcement. Reduced ResponsesThe Census Bureau’s chief scientist concluded the question would cause more than 2 million households, representing about 6.5 million people, to fail to respond to the census questionnaire. The bureau said statistical modeling techniques could use existing government data to produce more accurate citizenship information.But Ross rejected that analysis, saying the best approach would be to combine that existing data with information collected from the citizenship question. The Census Bureau has since increased its estimate of the number of people who won’t respond.The administration contended that courts lack any power to review Commerce Department decisions about what questions to include on the census.The Constitution requires a decennial census -- or an “actual Enumeration” -- but doesn’t provide any guidance about what information should be collected. Census-takers started asking about citizenship in 1820 but haven’t posed the question to every household since 1950.The Supreme Court Thursday rejected arguments that the citizenship question violates the “actual Enumeration” clause because it will lead to a less accurate count.The case is Department of Commerce v. New York, 18-966. To contact the reporter on this story: Greg Stohr in Washington at gstohr@bloomberg.netTo contact the editors responsible for this story: Joe Sobczyk at jsobczyk@bloomberg.net, Laurie Asséo, Ros KrasnyFor more articles like this, please visit us at bloomberg.com©2019 Bloomberg L.P.