Many URMs may not be "decendants of slaves" (not of any importance one way or another)
And it's not meant to "make-up" for slavery or anything else.-Just to reflect that they are under represented.
Afterall if it were meant to mean that, then why would a fresh immigrant from Africa who is black be treated 100% the same as the decendant of a slave? Answer: It obviously has no impact in any way whatsoever.
You can't separate underepresentation from past discrimination, the two are not mutually exclusive. When affirmative action programs gained steam in the late 60's and early 70's the entire idea was to make up for past discrimination. There was a recognition that African Americans' underepresentation in higher education was directly tied to historical prejudices. (Check out the background info in Bakke
The idea of affirmative action as a means to promote "diversity" (that is, actively seeking to admit underepresented minorities regardless
of past discrimination) is relatively new, and didn't get fully recognized until Grutter
The OPs question was why aren't North Africans considered "African American" for the purposes of law school admission? That's the specific question I was addressing. The answer is because "African American" has a specific meaning; it describes black Americans of African descent. Those Americans were denied access to education for hundreds of years, which resulted in underepresentation. That is why the term "African American" does not simply describe any person from the African continent who now lives in America.