Should a state be allowed to set, as a condition for out of state firms to do business, that they consent to being sued there in disputes with no relation whatever to the state? Today in Mallory v. Norfolk Southern Railway Co. the Supreme Court said “sure.” That’s likely to set off a boom in forum-shopping lawsuits at the expense of both economic rationality and fairness — and yet it’s also a plausible reading of the Court’s precedents on personal jurisdiction. Hence the Court’s deep split today, which crossed ideological lines.

The Court’s previous development of sound rules for personal jurisdiction has been one of its great successes of recent years and has materially rolled back many excesses of the previous litigation explosion. On the other hand, consent matters — matters so much, in fact, that it can sometimes require swallowing doubts about fairness of outcomes. That’s a lesson of the Court’s successful jurisprudence on arbitration — though that same lesson is rejected by many of those cheering today’s outcome.

Justice Alito’s concurrence notes that the Dormant Commerce Clause, which itself has been shrinking in application lately, might offer a way to stanch the practical damage. We should look for other ways too.