Judges on the U.S. Court of Appeals for the Second Circuit cast doubt on the use of service awards in class action settlements Tuesday, saying the basis for such fees for class representatives is “at best dubious” under U.S. Supreme Court precedent.

In the underlying case, Judges Dennis Jacobs, Pierre Leval and Michael Park upheld a $5.6 settlement between Visa and Mastercard and a class of 12 million U.S. merchants who challenged the way the credit card companies set and collect interchange fees. The deal included $900,000 for the eight lead plaintiffs.