In an antitrust decision from the mid-1980s, Nabanco v. Visa, interchange fees were upheld. But that decision was heavily fact-based, and many of the factual and economic conditions underlying it have changed.
Nabanco, an independent merchant processor, had sued Visa, arguing that interchange fees were illegal price fixing. The court rejected the claim for several reasons, each of which is severely weakened today. At the time, credit cards were still in their infancy and accounted for only a relatively small number of transactions. Consumers were just getting used to using credit cards, but cash and checks were the preferred method of payment. ATM networks appeared to be a potential strong rival.