A federal appeals court judge called on his colleagues on Monday to step into a growing class action debate that has reached the U.S. Supreme Court.

On a 2-1 vote the U.S. Court of Appeals for the First Circuit declined to take up an interlocutory appeal to overturn class certification in a class action brought over the labeling of Dial Corp.’s antibacterial soap. But in a dissent, Judge William Kayatta warned his colleagues that the court’s recent precedent over how class members could be identified was destined to result in “further mischief” that could challenge the constitutional rights of defendants. The dispute, referred to in the class action bar as “ascertainability,” is particularly important in a growing number of cases involving cheap goods for which most consumers don’t have receipts — such as Dial’s antibacterial soap.