Judge didn't hint outcome in oral arguments. Unresolved questions - including legal standing - about ability to appeal.
Federal judge throws out Durbin Amendment's 21-cent cap in emphatic ruling.
The National Retail Federation announced last week that it will formally oppose the final settlement of litigation between retailers, Visa and MasterCard and a number of the largest card issuers.
Latest round in battle between card brands and retailers seeks rejection of interchange settlement.
The retail group, which had not been part of the original litigation, had been criticizing the settlement for months.
The pending anti-trust settlement, pitting the six major card issuers and two major card brands against the retailers, has sparked a legislative backlash.
Card, retail executives say practice unlikely to take root in U.S.
The multiple-party, multiple-year case over credit card interchange moved one step closer to resolution on Nov. 9 when the Honorable Judge John Gleeson granted preliminary approval of the settlement agreement between retailers, payment networks and nine major card issuers.
Decision can still be appealed and National Retail Federation said it's considering that route.
Both sides of testy dispute issue statements ahead of New York hearing.