The Office of the Law Revision Counsel of the United States House of Representatives publishes the United States Code on the Web.

Even though it's free, be mindful of how current the published Code actually is (or is not). New laws are enacted all the time, so you need to update your research. Information about how to check for updates is provided, but it can become confusing if you are not an experienced legal researcher.

You'll see that the U.S. Code as published by the House of Represenatives carries this disclaimer:

"Every effort has been made to make this database accurate. Nonetheless, if you are using it for legal research, we urge you to verify your results with the printed U.S. Code available through the U.S. Government Printing Office."