Dirty Harry is the best law movie of all time. Bar none.
Inherit The Wind was also pretty cool, dramatizing the 1925 Scopes monkey trial (so-called), in which a teacher in Tennessee was convicted of teaching evolution in a high school science class. I don't think it's entirely true to history, but it's a pretty good flick for 50 years ago.
I liked the Paper Chase TV series, but I've never managed to stay awake through the movie.