I believe these Latin phrases are understood by many people, regardless of whether they've been to law school:
arguendo
caveat emptor
nunc pro tunc
qui tam
in rem
per curiam
ex parte
sine qua non
sic
pro bono publico
res judicata
res ipsa loquitur
in pari delico

'sic' and 'caveat emptor' yes, but i don't know about those other ones. i can't remember any lay person ever using 'nunc pro tunc' - at least not in my presence ;)

An even greater issue in intellectual and psuedo-intellectual company is pronunciation. See Fowler's Modern English Usage, pp. 167-168, where he points out the following in his entry on "false quantity":

"The simple fact is that in determining the quality of a vowel sound in English classical quantity is of no value whatever; to flout usage and & say Sõcrates is the merest pedantry."

Everyone is familiar with the fact that practice of the law includes use of many Latin words and maxims (see, it's even there!). But how did that come to be? Isn't English common law the foundation of Western law? I'm surmising that Latin was once the language of English common law and the Latin phrases found in the practice of law today are simply remnants. Basically, the Romans conquered ancient Britain and gave it their tongue; the ancient Brits used it for a long, long time then it gave way to Early English and eventually modern English? Am I on track?

Chuck,

Your etymological theory sounds entirely plausible. Roman law descended from Greek law, and was passed throughout the Roman Empire. This empire spanned, as you mentioned, throughout the various British Isles. Latin, the language of the Church, reined supreme and permeated all the provinces controlled by the Romans.

Another possible theory that sheds light as to why Latin is such an entrenched language within the law, is that Latin was given even special importance by the Holy Roman Empire. This successor state to the empire, founded in 800 by Charlemagne, was primarily a Germanic entity, but it had direct ties to the pope and a fairly wide reach throughout Europe. According to linguists, Western Germanic is the mother tongue of English, and the nexus of these circumstances may also account for Latin's prominence within the English language.