It would be easy to write off TCF National Bank vs. Ben S. Bernanke and the Federal Reserve as nothing more than politically motivated courtroom grandstanding by the banking company's chairman and CEO, Bill Cooper. But Minnesotans who care about free enterprise and a healthy banking system should hope Cooper prevails with the lawsuit TCF has filed against its regulator over debit-card transaction fees.

In its regrettable haste to punish the banking industry for the subprime mortgage mess and other mischief, Congress tacked on a provision known as the Durbin Amendment to the Dodd-Frank financial reform act, which President Obama signed into law in July. The amendment, sponsored by Illinois Democrat Richard Durbin, authorizes the Federal Reserve to greatly limit how much banks with assets of $10 billion or more -- including TCF -- can charge retailers for debit-card transactions. These so-called interchange fees have averaged about 1 to 2 percent of every transaction. Because of the growing use of debit cards, the fees produce tens of billions of dollars a year in revenue for banks.

Last week Star Tribune reporter Chris Serres described in stark detail how TCF's business model could be severely damaged if the Federal Reserve goes forward with the changes. The regional banking company estimated in court documents that its yearly revenue from interchange fees would shrink from $100 million to around $20 million, and that its return on equity would fall from 12 percent to less than 8 percent.

Consumers who hear the word "fee" in connection with banking understandably get queasy. There are, however, legitimate costs involved in processing financial transactions. The banking industry essentially built the debit-card system for retailers, and card use has mushroomed because consumers and retailers benefit from the security and flexibility of electronic payments while banks take on the risk of nonpayment.

Retailers reap the benefits of the Durbin Amendment, with the large banks covered by the provision no longer able to charge enough to cover their costs or make a profit. With no regard for the value of fair competition, Congress picked sides instead of letting the marketplace determine the value of this service. It's no wonder Walgreens, with its headquarters in Durbin's home state, joined Minneapolis-based Target and other retailers in aggressively lobbying for the amendment.

The amendment's arbitrary threshold of $10 billion in assets is another blow to fairness. Instead of limiting its punishment to giant banks with trillions or hundreds of billions in assets, much smaller regional operations such as TCF that serve the heartland will lose their ability to cover interchange costs. The TCF suit argues that the amendment violates the equal protection clause of the U.S. Constitution because it only affects about 60 large banks, giving unfair advantage to more than 7,000 smaller banks. The suit also claims that the fee limits represent an unconstitutional "taking" of the bank's private property.

TCF did nothing to deserve the congressional retribution. While some banks were busily dealing in risky derivatives and irresponsible subprime lending, TCF was making conventional loans to small businesses in Minnesota and other Midwestern states. And when the credit markets seemingly dried up, a healthy TCF kept lending. Its reward? Membership on the list of banks targeted by lawmakers who were eager to be seen pummeling big banks.

Some proponents of the Durbin Amendment have described the great savings consumers can expect to receive now that merchants have won relief from the cost of doing business. Excuse our skepticism, but it's difficult to see how federally imposed price controls that distort the market will benefit consumers. Our guess: The 60 banks will find new ways to recover their costs from their customer-cardholders, and most retailers will pocket the government-generated windfall. In the long run, the biggest losers will be the consumers Durbin claims to represent.