If you need to consult a general Spanish-English dictionary, three choices include the Spanish Royal Academy’s online Diccionario de la Lengua Española, the Collins Spanish Dictionary (also available online), and the Oxford Spanish Dictionary. Below is a selection of law-specific Spanish-English dictionaries.
Avalos Legal Glossary/Dictionary Translator and Other Related Fields of Study: English/Spanish Spanish/English
Contreras and Leutwyler Spanish-English Compendium of Law
Dahl’s Law Dictionary: Spanish–English/English–Spanish (6th ed.)
Diccionario JurídicoDictionary of Mexican LawDictionary of Mexican Legal Terminology (Spanish-English)