According to the "MLA Handbook for Writers of Research Papers" (7th edition), citations for borrowed information typically include the author's last name and a page number, among other bits of information. Legal sources such as court cases do not contain authors, however, so they must follow different guidelines for parenthetical citation and the Works Cited entry.
In-text
The citation for a court case includes the name of the case, which is usually the principle people or groups involved in the proceeding. You should italicize the name of the case in the signal phrase or citation and abbreviate "versus" as "v." (without the quotation marks). For instance, a case titled Smith versus Cornell University should appear as Smith v. Cornell University (italicized) in the citation or elsewhere in the body of the paper.
Works Cited
The Works Cited reference gives more detail about the case and where you found it. The entry begins with the name of the case, not italicized. After a period, the volume number, name and page or reference numbers of the law report appear, ending with a period. Next comes the name of the deciding court and a period. Give the year of the case with a period next. Then give the publication information for the source, such as the title and publisher of the book or Web page, the medium of the publication (such as Print or Web, followed by a period). If the information was found on the Web, you'd then include the date you accessed the information in day-month-year format. The first part of the entry would look like this:
Smith v. Cornell University. 323 US 431-444. Supreme Court of the US. 1999.
The information about the book, Web page or periodical would follow.