Talk:Ranger/@comment-161.142.169.171-20200129184154/@comment-8506165-20200129200939

It's just an oddity of this version of D&D rules, presumably because the ranger class was primarily based on Tolkien's Rangers who were all good-aligned. It's not the only nonsensical alignment restriction - you have to be Lawful Good to be a paladin... even though a lot of the paladins you run into in BG are Paladins of Helm who's a Lawful Neutral deity.

Later D&D versions were more permissive with alignments but BG was made before they came out.