There are two major legal citation formats.
At the library, we only have The Bluebook.
The Bluebook was released in its nineteenth edition in 2010. The work is compiled by the editors of the Columbia Law Review, the Harvard Law Review, the University of Pennsylvania Law Review, and The Yale Law Journal. A new edition is released every five years and until the ALWD Manual was published in 2000, the Bluebook was the only national citation system that was widely recognized.
The ALWD Manual was created by the Association of Legal Writing Directors “because lawyers, judges, law teachers, and law students need a citation manual that is easy to use, easy to teach from, and easy to learn from." (ALWD Preface) The ALWD Manual is consistent with the Bluebook on most practices and is increasingly so with the fourth edition changes released in 2010.
If you are having difficulty determining the proper citation format, it may be helpful to search recent editions of law reviews to see how they did it. For Bluebook, try looking at the Columbia Law Review, Harvard Law Review, University of Pennsylvania Law Review, and Yale Law Journal because their editors compile The Bluebook. For ALWD, see the list of law reviews and journals using ALWD.