Notes on Finding Laws:
Session Laws - Compilations of session laws provide a chronological record of laws passed in specific time period. For example, in Congress, a session is a two-year legislative period. To see a law as it appeared on the day it was signed into law, use Session Laws. Statutes at Large is the official federal compilation of session laws.
Codes - To see a law as it has been incorporated into the body of laws and amended since the date of passage, use codes. The United States Code is the official compilation of federal laws.
Annotated Codes - Annotations provide links to related court cases, amendments to previous versions of a law, etc. As previously noted, annotations can provide help with assembling legislative histories.
In legal proceedings, it's important to cite official versions of codes and session laws. Codes published in sources like Westlaw Campus are useful resources, but are not generally considered "official texts. That said, they are generally accepted for most student work. In some instances, including the United States Code and the General Laws of Massachusetts, the print sources are still considered authoritative.