There are two primary uses for legal encyclopedias.
First, the articles can be quite useful as a general introduction to an area of law which is new to you. They provide more in-depth information than a legal dictionary, while being nearly as accessible and easy to use.
Second, encyclopedias are a way to find citations to cases and other useful materials on a particular issue. These two uses make the encyclopedias a very good place to begin major research, whether for an academic paper or a legal memorandum. However, the legal encyclopedias are not intended to be used as authoritative sources on the law in any area, and thus are not cited in briefs, memoranda, or scholarly papers.