The last-minute collapse of a legal settlement between retailers and payment platform operators could set the stage for a new showdown over credit card processing fees. Shortly before the Memorial Day weekend, a group of major retailers opted out of the antitrust settlement first proposed by Visa and MasterCard during the summer of 2012. In response, Visa and MasterCard have filed a countersuit designed to confirm that industry standard "swipe fees" don't meet the definition of anti-competitive activity.

The settlement offer has already led to changes in many merchant processing practices, such as enabling retailers to set transaction minimums and permitting point-of-sale software to "steer" transactions to the least expensive forms of payment. The proposal has even opened the door to credit card surcharges on certain types of transactions, effectively passing along processing costs to customers in states that haven't yet banned the practice.

However, representatives from the National Retail Federation told reporters that the settlement offer doesn't go far enough to make merchant processing fees more competitive for its members. Walmart, Target, and Macy's all formally rejected the settlement offer, joining other retail coalitions that had previously opted out of the deal.

According to court documents, plaintiffs faced a May 28 deadline to accept the proposal or to reject the deal and seek their own resolution. NRF officials said that smaller retailers still attached to the settlement deal may lack the legal expertise to opt out of the settlement on their own, potentially setting up a scenario where their acceptance of the deal could validate new rates and regulations for all merchants.

Rather than wait until the anticipated September settlement date, Visa and MasterCard filed a complaint in U.S. District Court, asking a Brooklyn judge to confirm that the process of setting merchant processing fees does not constitute anti-competitive behavior.

Under current rate plans, most merchants pay fees ranging between 1 and 4 percent of each sale transacted with credit cards, plus monthly fees for technology and account maintenance. Credit card issuers have stated that interchange fees help pay for enhanced fraud prevention, customer service programs and rewards credit card benefits.