Legal Language

I’m listening to an interview of Bryan Garner on Slate.  I will admit to not having heard of him before this interview (I’m not a lawyer, nor do I play one on TV), but I had heard of one of his primary works: Black’s Law Dictionary (he evidently serves as the primary editor).  Language is a recent (or perhaps a long term) fascination and out of the gate on the podcast (first 2 minutes), the claim is made that Lawyers are required to be masters of English language.  Having just read Hasnas’ “Myth of the Rule of Law” (another Porcfest suggestion), I have to wonder for what purpose?  Is it clarity or obfuscation?