A legislature usually has neither the time nor the expertise to administer all of the details of a particular statute. It may, for example, pass a statute mandating clean water. However, it delegates the authority to actually implement the statute to a government agency such as the United States Environmental Protection Agency. Agencies issue administrative regulations to implement the details of the "enabling legislation" that gave the agency authority to act. The challenge with the executive branch is to track down the rules and regulations of federal and state administrative agencies.

Regulations, or rules which are issued by state or federal administrative agencies are published on business days in the Federal Register and then by subject in the Code of Federal Regulations (CFR).  You can find regulations at the GPO Access website and at agency websites.