Pronunciation of "parol" in Parol Evidence Rule

I have consulted several dictionaries. All of them say that the preferred pronunciation of "parol evidence rule" is "puh-ROLE EV-i-dence RULE," although some say that "PAH-role EV-i-dence RULE" is an acceptable alternative. The only entry I found that prefers "PAH-role," is the one in Merriam Webster that deals with the word "parol" by itself.

Until Wednesday, I never heard a lawyer or a law student pronounce it as "PAH-role"--but maybe I have led a sheltered life.