Usury laws prohibit lenders from charging interest rates above a certain level.
You can find a chart of the usury laws for all 50 states in the CCH Consumer Credit Guide (volume 1), in the National Survey of State Laws (under the heading "Interest Rates") and in the CCH Federal Banking Law Reports (paragraph 64-052). The two CCH sets are available in print and through Intelliconnect.
The usury laws for each state are part of each state's statutory Code. You can also find them in the CCH Consumer Credit Guide and the CCH Federal Banking Law Reports (paragraph 64-053), both available in print or through Intelliconnect. Or you can find them
IMPORTANT: California has exceptions to its usury laws that are often left out of the books. These include California Corporations Code Section 25116, 25117 and 25118, which exempt qualified securities from the usury laws.