President Donald Trump's proposal for a 10% ceiling on credit card interest rates has been met with opposition from academics who believe it is an attempt to reward the improvident at the expense of the provident and plunder the federal treasury. The proposal has been greeted with surprise and horror by academics, who believe that it is a medieval practice of usury laws, which were once a practice that was condemned in Economics 101 textbooks. The author argues that until 1979, all states had such laws limiting permissible interest rates on transactions within their domain. However, the Supreme Court recently discovered that a provision of the National Banking Act of 1863 forbade states from applying their usuries laws to national banks incorporated elsewhere, even to transactions involving their own citizens. Despite this, the author acknowledges that credit card companies charge off as losses roughly 4.1% of credit card loans, while credit grantors enjoy estimated margins of 10% on their credit card business. The article concludes that credit-granting banks enjoy net interest margins of about 10%.