On Thursday morning, the Supreme Court issued its opinion in one of the most important cases of the year. The Court decided Department of Commerce v. New York, regarding the Trump Administration’s effort to restore to the decennial census the simple question of whether a person is a citizen of the United States.

As I wrote last year, if you asked most people whether the federal government learns the number of citizens in the United States after each census, they would answer yes. After all, that’s one of the main purposes of the census.

From 1820 to 2000 a version of the citizenship question was asked in every census but one (in 1840). After the 1950 census, the Census Bureau decided to create two census forms—a short, basic form that all households would receive and a long form (which about 1/6 to 1/4 of households would receive) that would ask all of the information that the federal government needed. Thereafter, the citizenship question remained on the long form until the long form was terminated after the 2000 census. At that point the long form was replaced by the annual American Community Survey, which still contains the citizenship question. But only a tiny percentage of the population receives it.

The Trump Administration in early 2018 made the entirely-correct decision to restore the citizenship question to the census. That decision triggered hyperventilating on the Left, as well as a lawsuit from blue states that made three basic arguments: that restoring the citizenship question was unconstitutional, that it violated the Census Act, and that it did not comply with the arcane requirements of the Administrative Procedure Act.

The Supreme Court has now ruled. In a rational world, the Court would have issued a 9-0 decision rejecting each of these arguments. Instead, the Court ruled by a narrow 5-4 vote that asking the citizenship question was consistent with both the Constitution and the Census Act. But on the third question Chief Justice Roberts joined the four liberal Justices to hold that the explanation offered by the Commerce Department for reinstating the question was “arbitrary and capricious” because it was “pretextual.” This, he wrote, violated a requirement of the Administrative Procedure Act. The Commerce Department now has the opportunity to present additional reasoning behind its decision.

The claim that the Commerce Department’s explanation was pretextual is based on the fact that it justified restoring the question by pointing out that citizenship information would allow the Justice Department to better enforce the Voting Rights Act. However, the record of the case indicated that other reasons might have motivated the Commerce Department as well.

And that is hardly surprising. There are so many additional reasons for the United States to know how many citizens it has, that it is difficult to select any single one as the most important. Here’s my list:

The number of citizens is something that every sovereign country should know . Canada, Mexico, France, Germany, the United Kingdom, and dozens of other modern countries ask the question. It would be absurd if the most powerful and advanced country on Earth remained willfully ignorant of how many citizens it has. The principle of one person, one vote is at stake . Right now, state and federal legislative districts are drawn up simply based on the number of warm bodies in each district. Not only are legal aliens counted, but illegal aliens are counted too. As a result, citizens in a district with lots of illegal aliens have more voting power than citizens in districts with few illegal aliens. The assumption behind moving the citizenship question to the long form turned out to be wrong . It was hoped in the 1950s that a recent federal statute requiring all aliens to register and notify the federal government whenever they moved would be followed and enforced. That data could be substituted for the information lost by moving the citizenship question to the long form. However, the assumption turned out to be incorrect. The registration statute has become a bad joke: the aliens don’t comply, and the feds make little effort to enforce it. The citizenship question provides important information about voting . Knowing who is a citizen and who isn’t allows the government to make a more accurate determination of what percentage of eligible citizens are voting in each state and each county. It yields a wealth of valuable information about immigration . The question allows the government to determine which regions of the country see greater naturalization rates among aliens. This in turn reflects the assimilation of aliens into the American community. Citizenship data also enables the government to better calculate the number of illegal aliens in the country. Right now, estimates range from 11 million to 30 million. The open-borders Left doesn’t want the American people to know the true number.

And the list goes on. The point here is that there are numerous, perfectly-valid reasons to restore the citizenship question to the census. The fact that the Commerce Department chose to focus on only one does not in any way suggest that the Department acted arbitrarily or capriciously.

As Justice Thomas correctly wrote in dissent, “[A]n agency action is not arbitrary or capricious merely because the decisionmaker has other, unstated reasons for the decision.” He continued, “In short, the evidence cited by the Court establishes, at most, that leadership at both the Department of Commerce and the DOJ believed it important—for a variety of reasons—to include a citizenship question on the census.” Exactly.

Unfortunately, Chief Justice Roberts and the liberal Justices have required the Commerce Department to provide additional information to the District Court. But time is running out to get the census forms printed, and the opposing litigants and deep state bureaucrats will do everything they can to prevent the Commerce Department from acting quickly. Hopefully the Trump Administration will win the race. If they don’t, the whole country loses.

Kris W. Kobach was a professor of constitutional law during 1996-2011 at the University of Missouri-KC. He is currently is the General Counsel of We Build the Wall. He served as the Secretary of State of Kansas during 2011-2019. An expert in immigration law and policy, he coauthored the Arizona SB-1070 immigration law and represented in federal court the 10 ICE agents who sued to stop Obama’s 2012 DACA executive amnesty. He also served as U.S. Attorney General John Ashcroft’s chief adviser on immigration law and border security.