Here's the explanation of how to cite a law in the APA/MLA format. (I believe it supports what Glenfarcias says.)
"In the reference list entry, include the source and section number of the statute, and in parentheses, give the publication date of the statutory compilation, which may be different from the year in the name of the act. (Publication Manual of the APA, 2010, p.219)
Energy Policy Act of 2005, Pub. L. No. 109-58, 119 Stat. 594 (2005).
Explanation: In the example above, Pub. L. No. 109-58 refers to Public Law number 58 from the 109th Congress, as it appears in volume 119, page 594 of the US Statutes at Large (119 Stat. 594).