Article One of the United States Constitution
Congress has the power to borrow money on the credit of the United States. In 1871, when deciding Knox v. Lee, the Court ruled that this clause permitted Congress to emit bills and make them legal tender in satisfaction of debts. Whenever Congress borrows money, it is obligated to repay the sum as stipulated in the original agreement. However, such agreements are only "binding on the conscience of the sovereign", as the doctrine of sovereign immunity prevents a creditor from suing in court if the government reneges its commitment.