I have written this piece for Slate. It begins:

At Supreme Court oral argument in the Texas social media case back in February, Justice Samuel Alito asked the question: “Let’s say YouTube were a newspaper, how much would it weigh?” In Monday’s Supreme Court opinion in Moody v. NetChoice, a five-justice majority over Alito’s objection did not directly answer that absurd question, but it did say that under the First Amendment, Facebook should get about the same amount of editorial discretion as the Miami Herald. And that’s some good news from an otherwise bleak end of the Supreme Court term….

That’s where the agreement among the justices ended. Speaking for herself, Chief Justice John Roberts, and Justices Amy Coney Barrett, Brett Kavanaugh, and Sonia Sotomayor, Kagan gave guidance on where the 5^th Circuit went wrong in its First Amendment analysis in considering the constitutionality of the Texas content moderation decisions. None of this was necessary for the decision (in legal parlance, it was “dicta”), but the court addressed the issue because “[i]f we said nothing about those views, the court presumably would repeat them when it next considers NetChoice’s challenge.” The other justices would not have reached the First Amendment merits, although Alito expressed some serious reservations about the analysis.

Kagan’s guidance relied heavily on a 1974 case, Miami Herald v. Tornillo, in which the court held unconstitutional a Florida law that required newspapers to print the reply of someone who had been criticized in the newspaper. The court held that private actors like newspapers have every right under the First Amendment to include or exclude content as they see fit.

To Kagan, social media companies in moderating content were just like newspapers. She said that curating content is expressive activity protected by the First Amendment and that includes the decision to exclude content and that this principle is true even if most content is allowed and just a little bit is excluded. Further, when it comes to laws regulating speech, “the government cannot get its way just by asserting an interest in improving, or better balancing, the marketplace of ideas.” Were the rule otherwise, Kagan asserted, the platforms could be forced by Texas law to carry bad content including posts that “support Nazi ideology; advocate for terrorism; espouse racism, Islamophobia, or anti-Semitism; glorify rape or other gender-based violence; encourage teenage suicide and self-injury; discourage the use of vaccines; advise phony treatments for diseases; [and] advance false claims of election fraud.”

Moody might seem like an unremarkable decision, consistent with long-standing First Amendment principles. And indeed, in an amicus brief in the cases that I filed with political scientist Brendan Nyhan and journalism professor Amy Wilentz and co-authored with Nat Bach and his team at Manatt Phelps, we argued that Tornillo is the right analogy.

But in endorsing this view of the First Amendment, the majority brushed aside a major argument made by Justice Clarence Thomas in earlier cases and by First Amendment scholar Eugene Volokh that social media companies should be treated differently because they function like “common carriers,” such as the phone company. Just like Verizon cannot deny you a phone because of what you might say using it, the argument is that Facebook had to be open to everyone’s view.

The court gives the argument the back of its hand, never even addressing it directly; Alito says the majority “brushes aside the argument without adequate consideration.” Thomas says the argument should still be pursued in the lower courts, but it’s squarely inconsistent with what the Kagan majority says in its dicta. Volokh too sees many unanswered questions and thinks there is still a chance for some parts of these laws to be upheld when the cases get back to the lower court….