Only certain phrases, like prima facie. No real knowledge needed, other than a direct translation of the phrase. Not, IMO, a reason to learn the whole language.
While not a reason to learn the whole language, lets be honest, there is NO good reason to learn Latin, because it is a dead language, it is a mental exercise that will also come into practical use in court room/legal situations where there are Latin phrases used quite often.
I could spend the time, instead, just memorising all of the Latin phrases used in legal situations, but that seems rather pointless, and will always leave you open to finding a new Latin phrase that you don’t know how to say. It will also leave you open to uttering phrases that you don’t really understand the meaning of.
For instance, even on the very little that I have learnt, I think I know why a mandamus order is so called. I understand that the ‘amus’ at the end indicates that it is a “we” verb conjugation of mandare (not entirely sure!) which is to commit or to order.
I would rather spend the time learning the basic fundamentals of the language than just parrot fashion some words.
The guy’s a fanatic. He’s taken a German textbook on Latin from the 1800s (http://books.google.com/books/about/A_practical_grammar_of_the_Latin_languag.html?id=GJgAAAAAYAAJ ) which, unusually, is about speaking as well as reading and writing, which, although we can never know EXACTLY how it was pronounced, is surely the way to learn any language, since all languages alive or dead are founded on the rhythms and sounds of speech (and how can you enjoy Latin poetry properly without an idea of its music)…and turned it into an audio course in a vast series of podcasts FOR FREE (although he asks for donations).
I gave it a go a couple of years ago and gave up, but I swear I will do it properly and see it through one of these days…