Due to the complexity of the legal domain, reasoning about law cases is a very complex skill. For novices in law school, legal reasoning is even more complex because they have not yet acquired the conceptual knowledge needed for distilling the relevant information from cases, determining applicable rules, and searching for rules and exceptions in external information sources such as lawbooks. This study investigated the role of conceptual knowledge in solving legal cases when no information sources can be used. Under such "unsupported" circumstances, novice and advanced students performed less well than domain experts, but even experts' performance was rather low. The second question addressed was whether novices even benefit from the availability of information sources (i.e., lawbook), because conceptual knowledge is prerequisite for effective use of such sources. Indeed availability of the lawbook positively affected performance only for advanced students but not for novice students. Implications for learning and instruction in the domain of law are discussed.