Congress has used the financial crisis as an excuse to regulate what it calls “predatory lending.” As so often happens, its new regulations have had unintended consequences.

A bank in South Dakota, in order to comply with the new rules, is charging 79.9 percent interest for one of its low-limit credit cards. The pre-regulation rate was 9.9 percent.

The Credit Card Accountability, Responsibility and Disclosure Act of 2009 makes it illegal to charge annual fees greater than a quarter of a card’s limit. For small-balance cards, the allowable fees are tiny now. That leaves banks with three options:

-1. Lose money. The Wall Street Journal correctly notes that “Banks can’t be expected to give money away, even if Congress is in the habit of doing just that.” So this option is unlikely.

-2. Stop offering low-limit cards. This will hurt people who need them, such as people with low incomes, people with bad credit records, and young people who are trying to establish a credit record.

-3. Charge higher interest rates to make up for the money lost in fees. This is exactly what is happening here with the 79.9 percent rate for a $250-limit card.

If the bank calculated correctly, the 79.9 percent rate will be roughly a wash compared to the earlier high-fee, low-rate policy. But different customers will be paying. The people who incur a lot of interest-rate charges are usually the people who can’t afford them. And they’ll be paying a lot more than they were before the CCARD Act.

People who can afford to pay their balances on time often don’t pay little or no interest interest anyway. The 79.9 percent rate doesn’t really affect them. And now their annual fees have gone way down. The CCARD Act is, completely unintentionally, a wealth transfer from poor people to richer people. Congress is actively hurting the very people it intended to help.