In a central passage of Roberts's opinion, as he jousts with whether the Trump administration complied with the strictures of how agencies ought to announce major policy rollbacks, the chief looks to two justices from a different era and different persuasions as his, Oliver Wendell Holmes Jr. and Hugo Black, to more or less make the point that the government is not supposed to be lazy and haphazard with big decisions. "Justice Holmes famously wrote that '[m]en must turn square corners when they deal with the Government,'" he writes. "But it is also true," he added, quoting from Black, "particularly when so much is at stake, that 'the Government should turn square corners in dealing with the people.'"

Roberts is far from a flaming liberal. But he does seem to care about good government--process, rules, the orderly administration of justice. And what binds both last year's census controversy, which was a tangled web of its own, and Thursday's DACA decision, is the Administrative Procedure Act of 1946, a bulwark of federal law that sets up much of the nation's modern bureaucracy. Rules and regulations, to say nothing of a president's policy preferences, rise and fall under it. Roberts goes through some of the principles the law establishes: "The APA sets forth the procedures by which federal agencies are accountable to the public and their actions subject to review by the courts"; it requires "reasoned decisionmaking"; agency decisions can't be "arbitrary" or "capricious." During the Trump years, the statute has been a thorn in the side of his administration in that the losses under it have been massive. According to the Institute for Policy Integrity, the courts have invalidated a vast swath of Trump's agency policies, largely thanks to the 1946 law.