Back on April 20, 2006, Eugene authored a post that began,

Sorry, Your Viewpoint Is Excluded from First Amendment Protection: That's what the Ninth Circuit holds today, as to student speech in K-12 schools, in a remarkable — and in my view deeply unsound — decision. (Harper v. Poway Unified School Dist.)
  Tyler Harper wore an anti-homosexuality T-shirt to school, apparently responding to a pro-gay-rights event put on at the school by the Gay-Straight Alliance at the school. On the front, the T-shirt said, "Be Ashamed, Our School Embraced What God Has Condemned," and on the back, it said "Homosexuality is Shameful." The principal insisted that Harper take off the T-shirt. Harper sued, claiming this violated his First Amendment rights.
  Harper's speech is constitutionally unprotected, the Ninth Circuit just ruled today, in an opinion written by Judge Reinhardt and joined by Judge Thomas; Judge Kozinski dissented. According to the majority, "derogatory and injurious remarks directed at students' minority status such as race, religion, and sexual orientation" — which essentially means expressions of viewpoints that are hostile to certain races, religions, and sexual orientations — are simply unprotected by the First Amendment in K-12 schools. Such speech, Judge Reinhardt said, violates "the rights of other students" by constituting a "verbal assault[] that may destroy the self-esteem of our most vulnerable teenagers and interfere with their educational development."

  But as so often happens with decisions by Judge Reinhardt, Reinhardt's word was not the last. Today the Supreme Court vacated Reinhardt's in an order that states in relevant part:

HARPER, TYLER C., ET AL. V. POWAY SCHOOL DISTRICT, ET AL.

. . . The district court . . . has now entered final judgment dismissing petitioner's claims for injunctive relief as moot [because Harper graduated from the school]. We have previously dismissed interlocutory appeals from the denials of motions for temporary injunctions once final judgment has been entered. See Pacific Telephone & Telegraph Co. v. Kuykendall, 265 U. S. 196, 205--206 (1924); Shaffer v. Carter, 252 U. S. 37, 44 (1920). In this case, vacatur of the prior judgment is also appropriate to "'clea[r] the path for future relitigation of the issues between the parties and [to] eliminat[e] a judgment, review of which was prevented through happenstance.' " Anderson v. Green, 513 U. S. 557, 560 (1995) (per curiam) (quoting United States v. Munsingwear, Inc., 340 U. S. 36, 40 (1950)) (alterations in original). The petition for a writ of certiorari is granted. The judgment is vacated and the case is remanded to the United States Court of Appeals for the Ninth Circuit with instructions to dismiss the appeal as moot. See United States v. Munsingwear, Inc., supra. Reported below: 445 F. 3d 1166.

Justice Breyer dissents.

  What does it mean? It means that Judge Reinhardt's opinion has been "taken off the books," and the Ninth Circuit has been ordered not to issue any more opinions in the case. At the same time, the case is now over because the student graduated, so the Supreme Court won't be hearing the case. "Clear the path" indeed. Thanks to Howard for the links.

  UPDATE: Oops, I see that Eugene beat me to it while I was drafting this. I guess I'll keep this post up given that it offers more details, but if readers would rather I delete it just let me know. Also, I have updated the post for readers who don't know what it means to "vacate" a decision.