It's not a real concept.. it's just a meme. There's no "pass" that will grant you anything, and if there is a black person who says such a silly thing to a white person it's just shenanigans. Still won't change the context of the white person using the N-word after that anyway, especially it's historical context in the US. Also what I surely find interesting is that I only ever hear white people talk about an "N-word pass"...