One of your first considerations is whether you need to examine only laws, only regulations, or both. Laws, or statutes, are introduced by Congress and must gain approval of both branches of Congress as well as the president. Most laws tend to be broad and sweeping in their language. Regulations are specific written requirements for enforcing laws, often developed by the agency responsible for carrying out the provisions of that law.
Regulations are usually far more detailed and precise.
Your next step will be to determine whether your legislation or regulations are at the federal or state level, because the sources will be different. If you are familiar with the legislative research process, the quick chart on pages 2 and 3 will allow you to quick identify the source you need to consult. If not, check Shepard's Acts and Cases by Popular Names . This includes both state and federal laws and will give you the date of passage, public law number, and, citations to the U.S. Statutes at Large and the U.S. Code . It will also provide dates and public law numbers for legislation amending that act.