Kit Roane has a good piece in Fortune this week about banks shuddering as the giant retailer shoulders in on their bread and butter cash transaction business.

But one big Arkansas bank could actually cash in on its Wal-Mart ties in the financial reform package moving through Congress, the Wall Street Journal reports.

The bank is Arvest Bank, the closely held regional lender that’s controlled by the Walton family that founded Wal-Mart.

The Journal reports that Sen. Blanche Lincoln, the Arkansas Democrat behind the push to crack down on bank derivatives trading, is backing a change that would exempt Arvest from rule changes that would force it to raise more capital.

Lincoln has beaten back strong Wall Street opposition to her rules on derivatives, which are expected to be threshed out in Congress today. She has spoken of proposing “real reform” and promoting “a financial oversight system that promotes and fosters the most honest, open and reliable financial markets in the world.”

But she is now pushing to raise by 50% the threshold at which banks would be subject to stricter capital rules, the Journal notes. Lincoln “believes the threshold should be high enough to ensure no bank in Arkansas is subject to these new rules on existing capital, which would hinder their ability to generate lending for consumers and businesses at a time when access to credit is already difficult to come by,” her spokeswoman tells the Journal.

Applying the rules as Lincoln proposes could save the billionaire Walton family $115 million, the Journal says.

As the piece points out, congressional back-scratching is hardly unheard of. It came into full view this spring when Nebraska Democrat Ben Nelson tried to create a derivatives loophole for Warren Buffett’s Berkshire Hathaway .

So no shocker here. But as Lincoln surely knows, this sort of coziness doesn’t do much to help the cause of “real reform.”