Q. Why can credit cards charge such high interest rates?

A. Credit card interest rates are regulated by the state where the issuer is headquartered or chartered, not by the federal government.

Most card issuers set up shop in Delaware, South Dakota or Utah, states with weak—or nonexistent—usury laws that place no cap on interest rates. However, under the Credit CARD Act that takes effect Feb. 22, rates can’t increase on existing balances if your account is in good standing; and if you’re hit with an increase, you can cancel your card and pay off the balance at the old rate.

Sid Kirchheimer writes about consumer and health issues.