This paper presents a model for decision-making in legal translation in which the definition of legal communicative parameters determines the role of translation itself and the conditions for adequacy in each situation. It is argued that translation-oriented legal lexicography must take account of such parameters in order to be effective. In the case of system-specific legal concepts, this entails comparative legal analysis with a view to establishing the acceptability of reformulation options. The context of institutional translation serves to illustrate the extent to which terminological resources meet translators' needs in this field. A quality assessment of entries on national legal terms from two databases (IATE and UNOGTerm) examines limitations with regard to content relevance and reliability, and supports recommendations for more tailored approaches to legal terminology management.