I've been following the argument here over the Supreme Court's decision regarding the inclusion of citizenship question, but I've been reluctant to weigh in because, frankly, the confusion is so great I didn't know where to start.
First of all, what happened in the case that reached the Supreme Court is that a number of individual states. counties, and cities brought a lawsuit in a federal district court in New York (i.e., a federal trial court), asserting that their populations would be undercounted if a citizenship question was included in the census because that would deter certain respondents from completing the census questionnaires. They claimed the Commerce Department had violated a statute, the Administrative Procedure Act, which sets forth rules for how federal agencies are to apply the discretion granted to them by Congress pursuant to other, substantive (i.e., as opposed to procedural) statutes.
A "bench" trial was held (i.e., at the request of all parties, the judge rather than a jury acted as the fact-finder), after which the judge determined that the rationale offered by the Commerce Department was inadequate to meet the requirements of the Administrative Procedure Act. The trial judge ordered the Commerce Department to provide whatever additional evidence was available in the Department's administrative record to demonstrate that it had in fact met the statutory requirements leading to the decision to include the citizenship question.
In addition, the judge approved a request by the plaintiffs for additional fact-finding beyond the Department's administrative record because the plaintiffs had demonstrated that they might be able to produce credible evidence that Secretary of Commerce Wilbur Ross had acted in bad faith when he instructed his subordinates in the Commerce Department to add the citizenship question. The judge authorized the plaintiffs to acquire additional information from the government and to have certain Department of Commerce and Department of Justice officials provide depositions.
At the conclusion of this additional fact-finding, the district judge ruled that the government's decision to include the citizenship question was based on a rationale that was "arbitrary and capricious" (namely, a now-apparently-abandoned claim that Secretary of Commerce Ross decided to add the question in response to a Justice Department request for information needed to enforce a civil rights law).
The federal government appealed the district judge's decision. Normally such an appeal would be heard by the circuit court of appeals with jurisdiction over the trial court, but the government made an extraordinary request that the circuit court appeal be skipped and that the Supreme Court review the judge's decision directly because it was essential that the litigation be definitively concluded before July 1 in order for the paper census forms to be printed.
The Supreme Court agreed that the request to bypass the circuit court of appeals was justified in view of the imminent deadline for printing the forms. The Court concluded that the evidence produced at trial did indeed demonstrate that the justification offered for the citizenship question was a pretext, and therefore that the rationale did not meet the requirements of the Administrative Procedure Act. The Supreme Court decision of June 27 does not end the litigation. It remanded the case to the district court for additional fact-gathering and conclusions of law consistent with the Supreme Court opinion; these in turn may be appealed depending on how the trial judge rules.
The lawyers for the Justice Department who argued the case before the Supreme Court—or the trial court, for that matter—were not responsible for developing the rationale offered by the Commerce Department for including the question. They simply presented the evidence provided by the Department from its administrative record and, during the Supreme Court appeal, argued that the evidence was legally sufficient to comply with the requirements of the Administrative Procedure Act.
Any additional evidence that the Department of Commerce produces will be part of the extended fact-finding by the district judge. He will also be able to consider evidence beyond the administrative record because the plaintiffs have made a strong showing that Commerce Secretary Ross acted in bad faith. It appears that Secretary Ross himself may now be required to provide a deposition in the case.
The Trump Administration reportedly may now offer a different rationale for the citizenship question. Note that if it does, the new rationale must be based on evidence collected from the existing administrative record of the Department of Commerce. It's not simply a matter of coming up with a new explanation: there needs to be a factual showing from the record that the new explanation was indeed the real reason for including the question.
The reason the lawyers who conducted the original litigation asked to be excused from further participation in the case is to avoid an ethical conflict of implicitly contradicting the evidence previously provided by the Department of Commerce which they presented to the trial judge.
Another approach President Trump and Attorney General Barr appear to be considering would be to abandon the New York litigation and use an executive order or some other as-yet-unspecified technique to require the citizenship to be inserted in the census. They might be able to end the current litigation in New York by doing that, but probably not another case that is awaiting trial in a federal court in Maryland.
And, of course, any executive order is likely to be challenged in new litigation as exceeding the president's authority—Congress by statute explicitly delegated the authority to determine the content of the census to the Secretary of Commerce—or as inconsistent with the requirements of the Administrative Procedure Act.
However, unless Congress changes the law, the Secretary of Commerce is still authorized to determine the content of the census. There is nothing to prevent the Commerce Department from starting a new process to comply with the rules specified in the Administrative Procedure Act, conclude that there is a valid reason to ask respondents whether they are U.S. citizens, and arrange to insert that question in the decennial census. Not next year's census, perhaps, but there is plenty of time to build a record that will stand up in court for the census that will be conducted in 2030.