American law can be federal or state, depending on the subject matter of the law.
The power to write laws in the USA has been divvied-up in the American Constitution. So, some legal issues can be described and the information would apply from Bangor to San Diego. If you can't find what you're looking for here, try the USA-wide Law Pages . But other matters are subject to state laws and, as such, may vary from state to state. On this page, you will find those articles which discuss the law as it applies only to District of Columbia.