Hi - first post from me (long time lurker). I agree with Marc Abrams and Philip Smith. I would even be more assertive - "asking" someone to leave implies that they have the control in the situation, and this is not the case (or shouldn't be). "Telling" them with the voice of authority that you have of taking that class seems more appropriate. Do you teach a regular schedule? If I were in your shoes, I would make plain that in MY classes (that are x,y and z), this behavior is not acceptable from anyone in these classes. If there are other classes available, direct the student to those classes. Let the other teachers know you have done this. You may find that in making your stance that the others follow.
This is not a matter of ego, but of safety. Sensei may have other reasons for not acting, so of course would recommend discussing with him/her first.
Other option is call this student out for ukemi when discussing a technique. Nothing like trial by fire and public humiliation to put one's skills into perspective.
There is another teacher in our school that took a very aggressive tone with the guy. He just out rightly avoids the guys classes. He drives by and if he sees him teaching, he leaves lol. I wouldn't technically be apposed to this becoming my situation as well.
Found out today from a junior student that he has been inviting newbie students to receive instruction from him outside of class. I haven't told Sensei this yet. But that might just put Sensei over the edge with their patience with him... he's a nutter I think.