Re: What do you do when a student is acting rudely in your class.
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.