While certainly not an infallible aid in the process of legal translation, glossaries -especially monolingual ones- can be useful in understanding the legal terms as used in the source text, which can make translation of the legal text into the target language easier and more accurate.

A colleague recently drew my attention to this monolingual English glossary of basic legal terms from the Ministry of the Attorney General (Ontario / Canada). The glossary can be accessed at:

http://www.attorneygeneral.jus.gov.on.ca/english/glossary

Because Canada is bilingual, a monolingual French version is also available at:

http://www.attorneygeneral.jus.gov.on.ca/french/glossary/