Obviously it was a good thing that it was banned, but I'm just wondering if it would technically be considered authoritarian.
As in, is any law that restricts people's freedom to do something (yes, even if it's done to also free other people from oppression as in that case, since it technically restricts the slave owner's freedom to own slaves), considered authoritarian, even if at the time that the law is passed, it's only a small section of people that are still wanting to do those things and forcibly having their legal ability to do them revoked?
Or would it only be considered authoritarian if a large part of society had their ability to do a particular thing taken away from them forcibly?
I think you are lost in the language. There are no absolute rights, in any legal systems. So any "law" necessarily restricts someone's "rights".
Therefore, you need to think about what "authoritarian decision" means, because if all law restricts someone's rights, all laws are authoritarian by your definition.
Also: terrible example to begin with.
I was about the comment a similar thing.
If having a law that restricts one's ability to do something is "authoritarian" then any law is authoritarian, because laws, by definition, determine what behaviour is and isn't allowed within a society.