The restrictions on travelers from certain majority-Muslim countries was approved last June by a five-member conservative majority deferential to President Donald Trump's power to decide who enters the country. And the administration has been anxious to move to the high court the legal battle over another issue that reflects its hard-line immigration policies.
A coalition of Democratic-led states, cities and civil rights organizations oppose the effort, saying the question is a political move that will intimidate households with ties to noncitizens and result in an undercount that will harm the nonpartisan goal of getting an accurate tally of everyone in the country.
The time frame for a decision will be tight, as the Census Bureau must know by the end of June whether the question may be included on the 2020 form. Arguments are scheduled for Tuesday.
Three lower-court judges, all nominees of President Barack Obama, have ruled that Commerce Secretary Wilbur Ross's changing renditions of why the question should be added violated federal laws about administrative process. Two of the judges said his actions would result in a census tally so incomplete it would thwart the Constitution's command to count the entire population every 10 years.
Ross notes that at least a subset of the country has been asked about citizenship in every census, that asking the question of all households would provide more accurate information and that it is needed for the Justice Department to protect minority voting rights.
The stakes could hardly be higher. The enumeration clause requiring a count of the nation's population every 10 years is "the very foundation of our democratic system," wrote Judge Richard Seeborg of California, one of those who ruled against Ross.
It determines the size of each state's congressional delegation. It informs how the electoral districts for those seats and others - down to local school board elections - will be drawn. It determines how billions of dollars in federal aid is distributed.
Critics - including experts at the Census Bureau who report to Ross - say that adding the question will mean more households containing noncitizens are likely to ignore a request for information. They've calculated it could mean an undercount of as many as 6.5 million people and cause special harm to urban areas and states with large immigrant populations.
"It shows how unusual this case is ... for three courts to say the same things," said Dale E. Ho with the American Civil Liberties Union, one of four lawyers arguing before the court on Tuesday.
Those judges, from New York and Maryland, as well as California, stopped only slightly short of calling Ross's explanations duplicitous.
Seeborg wrote that it was "highly implausible" that Ross's true reason for adding the question was the one he offered to the court.
Judge George J. Hazel of Maryland concluded that "the secretary concealed his personal efforts to solicit a legitimate rationale for the citizenship question."
Politicians have been more direct.
At a hearing last month lasting more than six hours, Democrats on the House Committee on Oversight and Reform scoffed at Ross's explanation that adding the question would provide information helpful in enforcing the Voting Rights Act.
"Mr. Secretary, you lied to Congress, you misled the American people, and you are complicit in the Trump administration's intent to suppress the growing political power of the nonwhite population," Rep. William Lacy Clay, D-Mo., told him.
The Trump administration hopes for a friendlier venue at the Supreme Court, where it argues that Ross' authority to add the question, rather than his motivations, is the proper legal question. That is, if judges have a role at all.
"Nothing in the record supports the district court's extraordinary charge that the Secretary of Commerce lied to Congress, the judiciary, and the public," Solicitor General Noel Francisco told the court in his brief.
He adds: "The secretary's decision to reinstate the citizenship question is committed to agency discretion by law and thus judicially unreviewable."
Ross considered the possibility that asking the question could result in an undercount or require additional steps to make sure households comply and decided it was worth the trade-off of having more detailed information about who is in the country, Francisco wrote. Those are the kinds of decisions Congress gives agency heads the power to make, he added.
Almost every decennial census between 1820 and 1950 asked a question about citizenship. But since then, it has not been on the short form sent to all households, and asked only of a smaller subset of the population.
Ross announced in March 2018 that would change. He wrote in a memo that his action was prompted by a request from the Justice Department, which said adding the citizenship question would help the department enforce the Voting Right Act, which protects minorities.
But a coalition of blue states, cities and counties, and civil rights groups immediately filed suit in courts across the country. They said Ross' action, which was opposite of the advice of Census Bureau officials, was arbitrary and capricious, in violation of the Administrative Procedures Act; that it violated the enumeration clause in the Constitution; and that it would deny equal protection by discriminating against minorities.
Evidence developed in advance of the trial cast doubt on Ross' version of events.
He wanted to add the citizenship question from the start of his time as secretary, memos showed. He met with immigration hard-liners such as former White House aide Stephen Bannon and former Kansas secretary of state Kris Kobach.
The Justice Department letter was, in effect, reverse-engineered. Ross solicited the department's intervention, which came after his office contacted then-Attorney General Jeff Sessions.
To the judges who reviewed the evidence, this seemed like a political process, not one designed to produce a census that would provide the most accurate and useful information.
In light of the evidence, wrote Judge Jesse Furman of New York, "the court can ... infer from the various ways in which Secretary Ross and his aides acted like people with something to hide that they did have something to hide."
Furman ruled that Ross's actions constituted a "veritable smorgasbord of classic, clear-cut" violations of the Administrative Procedure Act and that the citizenship question could not be added. Hazel and Seeborg concluded the same and also said the question would violate the enumeration clause by resulting in a less accurate count.
None of the three judges said they could determine that Ross intended to discriminate against minorities. The Supreme Court last fall blocked the states and groups that have filed suit from deposing Ross.
The court denied the administration's request to stop the trials, which Justices Clarence Thomas and Neil Gorsuch said they would have granted.
Gorsuch indicated he was receptive to the government's view that Ross' decision deserved great deference.
"There's nothing unusual about a new cabinet secretary coming to office inclined to favor a different policy direction, soliciting support from other agencies to bolster his views, disagreeing with staff, or cutting through red tape," he wrote.
That question of deference is likely to be central to the court's decision.
The briefing is lopsided in favor of New York, California and the others who challenged Ross's decision, with businesses, former federal judges, and five former Census Bureau directors in Democratic and Republican administrations among those asking the court to uphold the lower-court decisions.
But a coalition of Republican-led states told the court they wanted the question added because of the information it would provide, and "irrational fears" about a lower return rate cannot be the reason for finding such a question violates the law, they argue.
In the end, the case will test the willingness of the court to defer to the executive branch, which was at the center of the travel-ban arguments.
Francisco wrote that in their 132 pages of briefing, the challengers failed to provide a manageable standard of deciding when a Cabinet officer such as Ross has abused his discretion to make decisions.
But those challenging the census decision say the two cases should not be compared.
"The area of immigration, partially because it is tied so closely to foreign policy, has traditionally been an area where the executive has been granted great discretion," said Thomas A. Saenz, president and general counsel of the Mexican American Legal Defense and Educational Fund, one of the plaintiffs in the Maryland case.
"There is no such deference to the executive branch with respect to the census, which until this administration, had never been so blatantly politicized and manipulated for partisan gain."
The case is Department of Commerce v. New York.
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