I don’t “ban” evil alignments, but I discourage them without really good reason.
Over my career as a DM, I’ve run across a lot of players who want to play evil characters and end up breaking or killing games. They may be playing badly or take their evil alignment the wrong way or whatever, but the results are the same regardless: that the carefully crafted game falls apart, feelings often get hurt, and the fun shrivels up.
D&D isn’t easy to pull off sometimes, particularly as you get older and the logistics of getting everyone together get harder. So why take such a huge risk if it isn’t necessary for your game?
Evil alignments typically require an experienced, very mature, very respectful player to pull off. In the hands of an inexperienced or self-centered kind of player (a “but I was just playing my character!” type), the character is almost certain to mess up the game for everyone.
I suspect AL forbids NE and CE–only allowing LE, and then only if you’re Zhentarim–for similar reasons. It’s even more apt there, because you’re siting down with a table of strangers, and we’ve all heard stories about con games and the sorts of harassment that can come out of those. Even if no abuse is intended, it’s so easy to misunderstand the motives of strangers and have a really shitty time if they’ve acting up.
So, the answer is Probably, at least until you’re very comfortable with your game and your players.