Minecraft server question? Is this illegal?

[Tyler]

So a friend got an Owner of a minecraft server to op her by tricking him into thinking she was a famous youtuber (or at least that's what I think happened). So we banned the owner and some of the staff and kinda took over the server. We didn't use any hacks, so would this be illegal?
*cough troll* Anyway I do have my owner server bro. The owner was a jerk. I told her we should stop.
Also I know it was a dick move, I feel bad about it on my part.
Agreed. But I really need to know if this is illegal. It doesn't seem like it would be, but I need to know.
Mojang doesn't host servers...
Anyway we didn't exploit the software with hacks or anything. My friend just convinced the server owner to op her. I wouldn't think there's laws about who you can and cannot ban on minecraft