According to the Associated Press, the United States Supreme Court rejected T-Mobile's appeal in three related cases. The issue in the three cases is identical: whether state laws limiting class action ban clauses in consumer contracts are preempted by federal law. As of this posting, the Supreme Court docket does not yet reflect the denial of the Petition in case 07-976.
T-Mobile sought review of a Ninth Circuit decision that precluded enforcement of a class action ban on the ground that a recent "Third Circuit decision (Gay v. Creditinform) created a conflict among the lower courts." (Gupta, Supreme Court Refuses to Hear Class-Action Ban Issue (May 27, 2008) pubcit.typepad.com.) [Note: Public Citizen participated in the opposition to T-Mobile's petition.]
State and federal courts have been holding of late that class-action bans in arbitration clauses are unconscionable under state contract law, a result seen in the Discover Bank decision (Discover Bank v. Superior Court (2005) 36 Cal.3d. 148) in California. Defendants routinely argue that the Federal Arbitration Act preempts state law on this issue. However, that argument has not met with success; the Federal Arbitration Act expressly saves generally-applicable state contract law of unconscionability from preemption.
UPDATE: The May 28, 2008 Order List from the Supreme Court includes the Laster v. T-Mobile determination.