On June 18, the U.S. Supreme Court struck down the Trump administration's rescission of the Obama administration's immigration relief program known as Deferred Action for Childhood Arrivals (DACA). In explaining and then defending its DACA rollback, the Trump administration had raised an array of claims that, if accepted, would have undercut numerous regulatory rule of law fundamentals. Instead, the Court strengthened these longstanding requirements. Department of Homeland Security (DHS) v. Regents will become central to battles over the many Trump administration rollbacks and reversals of environmental and other regulations.

In the Trump DACA rescission, the administration relied heavily on an argument it has often deployed to justify regulatory rollbacks. It claimed that the Obama administration DACA policy was so legally flawed that the Trump team had no choice but to reverse the policy. And in this DACA rescission, like many of its environmental regulatory rollbacks, the Trump regulators provided little more than conclusory analysis of reliance interests flowing from the earlier action and similarly skimpy analysis of effects of the new actions. Similarly flawed approaches combining new disavowals of legal authority with skewed and often conclusory analysis of effects are especially evident in climate deregulatory actions and the "waters …