If you haven't had any classes with him, then no, find a professor instead. Law schools would much rather have a rec from someone who not only knows you, but knows your academic work. Unless you have no professor you think would give you a good rec (usually not the case, unless you've been out of school for a while, and I don't get the feeling that this fits you), then get one from the advisor. I think it'd be more beneficial for a prof though.