The term Generally Accepted Accounting Principles is abbreviated as GAAP. (Actually, I don't know if it is an initialism and each letter is spoken, or whether it is pronounced as gap, sorry.)
Now, I just read the phrase, "GAAP rules dictate that ... ." and noticed that if you expand the acronym, you get "Generally accepted accounting principles rules dictate that ... ", which is redundant since rules is a near-synonym of principles. The word was likely added by the writer only to make GAAP function like an adjective rather than the plural noun that to me it properly seems to be.
Would it be grammatically correct, then, to say "GAAP dictates that ..." and accept the mild discomfort with this construction that I feel as a native English speaker? Or is it better to ignore the behind-the-letters meaning and use it as the adjective it seems to "want" to be?
The link in my first sentence above does use the plural, though: "GAAP are a combination of authoritative standards ... ." So it is used in the plural sometimes.
I did read some other answers here that covered more specifically how to pluralize acronyms (such as "GAAPs dictate that ... ") but doubt that any in the relevant industry would think this acronym could properly take an s for pluralization.
Please guide me.