In the four months since the Supreme Court rejected the Trump administration’s cynical effort to add a citizenship question to the 2020 census, the decision — which the president came dangerously close to defying — has faded from view under the weight of all that has happened since. The census will proceed next spring in the usual way, without sorting the country’s population into citizen and noncitizen. That’s that, it would seem.

But the decision’s work is not done. Next Tuesday, the Supreme Court will hear arguments on the validity of President Trump’s decision to terminate the program that shields hundreds of thousands of young undocumented immigrants — the Dreamers — from deportation and allows them to live openly in American society. Chief Justice John Roberts’s 5-to-4 majority opinion in the census case, Department of Commerce v. New York, is playing an important although largely unnoticed role in how advocates are framing their arguments about the fate of the program, Deferred Action for Childhood Arrivals, known as DACA.

The court’s eventual decision in the case, Department of Homeland Security v. Regents of the University of California, is obviously of vital importance to the young people who in the seven years since DACA began have been able to study, work legally and start familie s. But the decision will also be important in defining the court’s relationship to a president who behaves as if he has the Supreme Court in his pocket. It will indicate whether the Roberts court — more specifically, the chief justice himself — will continue to insist on believable explanations from an administration that often appears incapable of giving one.

The parallels between the two cases aren’t exact, but they are striking. Adding the citizenship question to the census was part of the Republican strategy to suppress the response in immigrant-heavy communities and skew the data that feeds into redistricting. When challenged, the Commerce Department claimed it needed the citizenship information to help the Justice Department better enforce the Voting Rights Act, an explanation that Chief Justice Roberts said “seems to have been contrived.” It was, he observed, “incongruent with what the record reveals about the agency’s priorities and decision making process.”