Nexis Uni offers Shepard's citations for cases, regulations, and statutes.
A formal definition: "Shepard’s Citations provide a judicial history of cases and statutes, make note of new cases, and indicate whether the law in a particular case has been followed, modified, or overruled in subsequent cases... various abbreviations indicate whether a case has been overruled, superseded, or cited in the dissenting opinion of a later case."
"Shepard’s® Citations." Gale Encyclopedia of American Law. Ed. Donna Batten. 3rd ed. Vol. 9. Detroit: Gale, 2010. 176. Gale Virtual Reference Library. Web. 19 Aug. 2015.