I'll preface this brief post by noting that I have not had a chance to read the entire opinion, but the opnion in Walmart Stores, Inc. v. Dukes (June 20, 2011) was released this morning by the United States Supreme Court.  The Court reversed the Ninth Circuit and the District Court, finding that the matter was not suitable for class certification.  The core majority was authored by Justice SCALIA. ROBERTS, C. J., and KENNEDY, THOMAS, and ALITO, JJ., joined in that opinion, and GINSBURG, BREYER, SOTOMAYOR, and KAGAN, JJ., joined as to Parts I and III.  Justice GINSBURG authored an opinion concurring in part and dissenting in part.  BREYER, SOTOMAYOR, and KAGAN joined in Justice GINSBURG'S opinion.

Some key aspects of the holding are:

• Proof of commonality necessarily overlaps with respondents’ merits contention that Wal-Mart engages in a pattern or practice of discrimination. The crux of a Title VII inquiry is “the reason for a particular employment decision,” Cooper v. Federal Reserve Bank of Richmond, 467 U. S. 867, 876, and respondents wish to sue for millions of employment decisions at once. Without some glue holding together the alleged reasons for those decisions, it will be impossible to say that examination of all the class members’ claims will produce a common answer to the crucial discrimination question.
• General Telephone Co. of Southwest v. Falcon, 457 U. S. 147, describes the proper approach to commonality. On the facts of this case, the conceptual gap between an individual’s discrimination claim and “the existence of a class of persons who have suffered the same injury,” id., at 157–158, must be bridged by “[s]ignificant proof that an employer operated under a general policy of discrimination,” id., at 159, n. 15. Such proof was absent here.
• Claims for monetary relief may not be certified under Rule 23(b)(2), at least where the monetary relief is not incidental to the requested injunctive or declaratory relief.
• The mere “predominance” of a proper (b)(2) injunctive claim does nothing to justify eliminating Rule 23(b)(3)’s procedural protections, and creates incentives for class representatives to place at risk potentially valid monetary relief claims.

Justice Ginsburg is concerned that the majority imported too much of the "predominance" analysis into the Rule 23(a) requirement that common questions of law or fact must exist:

The Court’s emphasis on differences between class members mimics the Rule 23(b)(3) inquiry into whether common questions “predominate” over individual issues. And by asking whether the individual differences “impede” common adjudication, ante, at 10 (internal quotation marks omitted), the Court duplicates 23(b)(3)’s question whether “a class action is superior” to other modes of adjudication.

Slip op., Ginsburg concurring and dissenting, at 9.  Otherwise, Ginsburg agrees that the class should not have been certified under Rule 23(b)(2) but would  have saved the issue of whether certification was appropriate under Rule 23(b)(3) for the District Court on remand.

The opinion looks as though it will prove to have the greatest impact on cases of this type.  While the Rule 23(a) construction seems to be inconsistent with well-settled standards, the balance of the opinion was predictable, given the massive size of the class.