Revolt of the Junior Justices?

Among the four decisions handed down today was Dolan v. United States, which considered whether a sentencing court may order restitution despite missing the statutory deadline of 90-days after sentencing for restitution to be ordered.  The Court held, 5-4, that the answer is yes, “at least where, as here, that court made clear prior to the deadline’s expiration that it would order restitution, leaving open (for more than 90 days) only the amount.”

What’s particularly interesting about Dolan is the Court’s line-up.  Justice Breyer wrote the majority, joined by Justices Thomas, Gisnburg, Alito, and Sotomayor.  The Chief Justice dissented, joined by Justices Stevens, Scalia, and Kennedy.  This is neither a left-right nor formalist-pragamtist split.  There is a division in the case based upon seniority — the majority consists of the five junior-most judges — but I don’t see how that would influence the respective justices’ view of the case.

UPDATE: As a commenter notes below, this appears to be the first case in which Justice Thomas was the most senior judge in the majority (and therefore assigned the opinion).  Before the confirmation of Justice Sotomayor, Thomas could not have been the most senior justice in the majority, as there were five justices senior to him (the Chief, Stevens, Scalia, Kennedy, and Souter).