A federal appeals court has overturned a decision certifying a price-fixing class action over a deal to postpone sales of a generic version of GlaxoSmithKline’s epilepsy drug Lamictal.

The U.S. Court of Appeals for the Third Circuit’s ruling provides a refresher course on a judge’s gatekeeper role in class action suits. The panel found the lower court judge granted certification without properly analyzing whether issues common to the class predominate over individual issues.