I have written this piece at Slate. It begins:

At the end of his majority opinion for the Supreme Court striking down the Biden administration’s student loan forgiveness program, Chief Justice John Roberts stridently protested the scope and tone of Justice Elena Kagan’s dissent for the court’s three liberal justices. Kagan, pulling no punches, wrote that the court majority “violates the Constitution” by “exercis[ing] authority it does not have.” Roberts lamented the “disturbing feature of some recent opinions to criticize the decisions with which they disagree as going beyond the proper role of the judiciary.” In ruling that the Biden administration exceeded its powers, “we have employed the traditional tools of judicial decisionmaking,” Roberts contended, warning that the public should not be “misled” to read this “heartfelt disagreement” over which “reasonable minds may disagree” as “disparagement.”

Roberts’ bristling in Biden v. Nebraska over the dissenters’ temerity to claim that the six-justice majority crossed the line from legitimate application of judicial principles to a judicial power grab is more than a bit ironic. Just three days earlier in Moore v. Harper, Roberts wrote another majority opinion that sets up the Supreme Court and other federal courts to routinely ask whether state courts are crossing the exact same line in the most sensitive of political cases. Roberts’ reaction in Nebraska should have told him that this exercise of judicial legitimacy line-drawing in high-profile cases is folly and will lead to even greater polarization over the judiciary.

As I recently explained in Slate, in Moore the Supreme Court did more than reject a crazy theory that would have given state legislatures virtually unlimited authority to decide the rules for conducting federal elections. The court also held that federal courts (and especially the Supreme Court) can determine whether state courts have gone too far in their interpretation of state constitutions protecting the right to vote or in reading state election statutes applied to federal elections. It held that “state courts may not transgress the ordinary bounds of judicial review such that they arrogate to themselves the power vested in state legislatures to regulate federal elections.”

The court in Moore didn’t really explain what those dense words mean, but the test put forward by the Moore majority seems to require federal courts to look at the opinions of state courts exactly the same way that the dissenters in Nebraska looked at the opinion of the court majority in Nebraska. It asks one set of judges to judge the judging of other judges…

The majority in Nebraska did not like being characterized by the dissenters as usurping the judicial function and letting politics sweep in. But consider the kinds of questions that will come up under the test embraced in Moore. In Moore itself, the North Carolina state Supreme Court decided that partisan gerrymandering violated the North Carolina Constitution’s protection for “free and fair” elections. How will a federal court decide if that state court interpretation goes too far and “arrogates” power vested in state legislatures? Will the Supreme Court decide it is “arrogation” if the state court offers a novel interpretation of the state constitution? As Leah Litman writes, such a rule would serve to penalize interpretations of state constitutional provisions that protect voters that reach state courts for the first time…..