Information on citing legal sources in APA can be found in Appendix 7.1. APA relies on the The Bluebook: A Uniform System of Citation for formatting legal citations. Some examples are provided here; for more complex examples, consult The Bluebook.
Name v. Name, Volume Source Page (Court Date).
Example: Brown v. Board of Education, 347 U.S. 483 (1954).
Cited in text: Brown v. Board of Education (1972)
(Brown v. Board of Education, 1972)
Example: Ragas v. Tennessee Gas Pipeline Co., 136 F.3d 455 (5th Cir. 1998)
Cited in text: Ragas v. Tennessee Gas Pipeline Co. (1998)
(Ragas v. Tennessee Gas Pipeline Co., 1998)
Popular or official name of the act, source and section number of the statute (publication date of the statute).
Example: Mental Health Systems Act, 42 U.S.C. § 9401 (1988).
Cited in text: Mental Health Systems Act (1988)
All citations of the U.S. Constitution begin with U.S. Const., followed by the article, amendment, section, and/or clause numbers as relevant. The terms article, amendment, section, and clause are always abbreviated art., amend., §, and cl., respectively. Preamble is abbreviated pmbl. (as in my opening quotation). Article and amendment numbers are given in Roman numerals (I, II, III); section and clause numbers are given in Arabic numerals (1, 2, 3).
Example: U.S. Const. art. I, § 3.
Cited in text: (U.S. Const. art. I, § 3.)
Example: U.S. Const. amend. XIX
Cited in text: (U.S. Const. amend. XIX)