Evan Schuman's StorefrontBacktalk

Walmart really wants out of the $6 billion interchange settlement, and for a very specific reason: The world’s biggest retailer doesn’t want to be barred from suing Visa and MasterCard again. And the only way to preserve that right is to get enough big chains to bail out of the settlement.

But the real problem—Visa’s death-grip on payments—isn’t one any lawsuit will solve. Big retailers abandoned their store cards because taking Visa was cheaper than maintaining their own credit infrastructure. Now Visa is holding all the cards, and chains are unenthusiastic about any of the alternatives.

The settlement, which would also enable retailers to add a surcharge for payment-card transactions or to discount debit-card sales compared with credit-card sales, was designed to avoid an antitrust trial against Visa, MasterCard and card-issuing banks that was slated to start in September. Kroger, Walgreens, Publix and 15 other named plaintiffs initially agreed to the deal.

Walmart isn’t a named plaintiff in the proposed class-action settlement, just a retailer that falls into the settlement class. Ordinarily, that would mean the chain could simply opt out of the settlement, collect no money and preserve all its rights.

But according to Thompson Reuters legal reporter Alison Frankel, this settlement is as convoluted as you would expect from the people who gave us PCI. Under the rules for this particular class action, retailers can only opt out of their share of the $6 billion plus the eight-month reduced-interchange period—but not the limit on future lawsuits. “It’s the opposite of take the money and run: Give up the money and stay tied to the other terms of the settlement,” Frankel wrote.

That explains Walmart’s sudden full-court press to scuttle the whole deal. If it can get retailers who represent 25 percent of Visa and MasterCard’s dollar volume to reject the deal, the card brands can unilaterally declare the deal dead. Alternatively, if enough chains bail on the deal, the judge can reject the settlement and the massive case can continue to lurch toward a trial. But just the settlement approval or rejection will tie things up until at least early summer of 2013.

(For anyone who really wants to keep score, before any of that happens the court has to sort out the situation with the National Association of Convenience Stores. The Association is the only named plaintiff that objects to the settlement terms and has now changed lawyers to Constantine Cannon, the law firm that represented Walmart when it led the last big retailer interchange revolt, which resulted in a $3 billion settlement in 2004. Small world, huh?)

All these complications—and especially Walmart’s vehement opposition—make it increasingly unlikely that the settlement will survive as it currently stands. That means eventually the lawsuit will go to trial.

Trouble is, that’s almost certainly pointless for chains looking for interchange relief. They don’t need a verdict. They need competition in payments.

And that’s where the real conflict lies on the retailers’ side: U.S. retailers don’t much like any of the alternatives to Visa and the banks—or even alternatives to magstripe cards.