Source citations for case law, court decisions, law journals, and legislation have their own specialized style norms, and other citation style guides (APA, Chicago, MLA, etc.) typically defer to those norms instead of creating their own rules. In the United States, "the definitive style guide for legal citation" is the Bluebook's Uniform System of Citation (now in its 20th edition), and so it is to Bluebook guidance that other style manuals defer.
The David L. Rice Library does not have an institutional subscription to the 20th edition of the Bluebook online; we do have a print copy of the 19th edition (2010) in the Reference collection. Three more recent free online resources for creating Bluebook-style legal citations are linked below. Users already generally familiar with Bluebook style may also find that ZoteroBib can be useful for generating the basic elements of a legal citation. More advanced Zotero users may want to download and use Juris-M, a reference manager designed specifically for legal citation.