Suppose there had been a leak from the Supreme Court early Thursday morning: The court was about to issue its long-awaited decision in the DACA case on the fate of nearly 700,000 young immigrants known as Dreamers; the vote was 5 to 4; and the majority opinion was by Chief Justice John Roberts. But the leaker didn’t know, or wouldn’t say, which way the case came out.

Ladies and gentlemen, place your bets.

Among the Dreamers and their supporters, hearts would have been in their throats. This was the chief justice, after all, who two years ago wrote the opinion upholding President Trump’s Muslim travel ban, and who five years before that wrote the opinion dismantling the Voting Rights Act. The vote in both was 5 to 4. Why wouldn’t the conservative chief justice defer to the president’s decision to end a program, Deferred Action for Childhood Arrivals, that his predecessor had instituted by executive action without even seeking Congress’s approval?

But the president’s allies would have had ample reason to be anxious. Wasn’t this the chief justice who just a year ago wrote the majority opinion that by a vote of 5 to 4 blocked the president’s plan to add a citizenship question to the 2020 census? The proposal failed the essential requirement of administrative law for “reasoned decision making,” Chief Justice Roberts wrote in that case. He dismissed the administration’s proffered good-government rationale as pretextual; or, as the dictionary puts it, “dubious or spurious.”

Now, of course, we know that it was the Chief Justice Roberts of the census decision, which an enraged President Trump came within inches of defying, who arrived on the scene in time to save the Dreamers. His opinion assured readers that in holding that the administration’s effort to undo DACA was invalid, the court was not endorsing the program. That is conventional administrative law talk — and the case, as the chief justice framed it, was a conventional one about administrative procedure.

The administration’s explanation for why it was terminating DACA — explained in a single sentence by an acting secretary of the Department of Homeland Security (“Taking into consideration the Supreme Court’s and the Fifth Circuit’s rulings in the ongoing litigation, and the September 4, 2017 letter from the Attorney General, it is clear that the June 15, 2012 DACA program should be terminated”) — was so inadequate as to make the decision “arbitrary and capricious,” Chief Justice Roberts said.

While the department came up with a more elaborate explanation nine months later in response to an unfavorable Federal District Court ruling, the chief justice said that it was a “foundational principle of administrative law” that an agency, once challenged, has to defend its action on the grounds it initially invoked, not on an after-the-fact rationalization, unless it wants to restart from scratch the process of arriving at a decision.

The dry procedural language of the opinion, including its invitation to the Trump administration to start over and find a new way to defend terminating DACA, seems to have lulled many readers into assuming that the victory for the Dreamers is less than complete. No doubt many eyes had glazed over by Page 24, when the chief justice began a crucial discussion of the “reliance interests” in favor of continuing the program that permits DACA recipients to live and work lawfully in the only country that most of them have ever known.

Citing statistics in briefs filed by, among others, a group of 143 businesses, Chief Justice Roberts emphasized that those with a stake in continuing the program included not only the Dreamers themselves but also their families, “including their 200,000 U.S.-citizen children,” “employers who have invested time and money in training them” and state and local governments that would lose tax revenue from DACA recipients’ earnings.

Administrative law requires the agency to take reliance interests into account, Chief Justice Roberts said. “DHS may determine, in the particular context before it, that other interests and policy concerns outweigh any reliance interests,” he said, adding, “Making that difficult decision was the agency’s job, but the agency failed to do it.”

And can the Trump administration do it now? Theoretically yes, under still another acting homeland security secretary, but any newly justified rescission announcement would find the administration back in court within hours, the clock ticking all the while toward Election Day. Although the chief justice nominally left it up to the administration to weigh the reliance interests against its policy goal, his exposition of the strength of those interests sets a very high bar for this or any subsequent administration to clear.

Where was the other Chief Justice Roberts this week, the one of the disastrous Shelby County v. Holder voting rights decision and of the travel ban decision? Was the Chief Justice Roberts who silently joined Justice Neil Gorsuch’s majority opinion bringing L.G.B.T.Q. people within the protection of federal anti-discrimination law the same chief justice who wrote a snarky dissenting opinion five years ago when the court upheld the constitutional right to same-sex marriage?

Contemplating this head-snapping week at the Supreme Court, I’m reminded of the amazing 2002-2003 term, when the court under another conservative chief justice, William Rehnquist, seemed to pull its robust conservatism up short. In the space of a few weeks in the spring of 2003, the court upheld affirmative action in higher education; granted constitutional protection to gay men and lesbians for their private sexual lives; and upheld the application of the family-care provision of the Family and Medical Leave Act to state employees.

Chief Justice Rehnquist himself was in dissent in the first two of those cases, but he surprised nearly everyone by writing the majority opinion in the third, a case that may sound obscure now but that effectively spelled an end to the federalism revolution on which, under the chief justice’s leadership, the court had been embarked.

What could have accounted for that surprising turn of events at the dawn of the new century? Wrestling with that question, I eventually concluded that the court was realigning itself, as it has done historically, with its own sense of what the public wanted and expected from it.

“No great Supreme Court case is only a question of law,” I wrote then. “It is always also an episode in the ongoing dialogue by which the court engages with the society in which it operates and in which the justices live.”

Just so with this week’s cases. Monday’s ruling on the right of gay and transgender people to be free of discrimination in the workplace showed a court that by a refreshing vote of 6 to 3 decided not to stand in the path of a tide of social change. The DACA decision contained a message threaded through its dry language of administrative procedure — a warning to the Trump administration not to assume that it gets a free pass, not to take the Supreme Court for granted.

“This is not the case for cutting corners,” the chief justice wrote. That’s a sentence sure to be echoing in the halls of the solicitor general’s office, where Chief Justice Roberts once worked and where he honed his ability to speak to the Supreme Court. Now, with four colleagues to his left and four to his right, he speaks for the court from a center chair that must often feel like a lonely place.

Given the decisions due in the next few weeks on abortion, religion, the president’s tax returns and the Electoral College, among other cases, it’s too soon to place a label on this pandemic-disrupted Supreme Court term. The justices will issue decisions that will infuriate, reassure, surprise and even break hearts, as they evidently broke Senator Josh Hawley’s on Monday. The Missouri Republican took to the Senate floor to bemoan “the end of the conservative legal movement.”

But as the ambitious young senator, a former law clerk to Chief Justice Roberts, surely knows, there is no end, only a new beginning.

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