Some supervisors are control freaks and expect you to ask them for permission whenever you do anything, irrespective of Postgraduate Regulations.

Make sensible decisions though.

I quit my PhD because my supervisor was intolerable and the University breached its own regulations, refusing to provide a new supervisor. All I got out of it was an apology, which is a lot more than most will get unless they're prepared for 1-3 years of litigation and a paltry payout.

I got out, couldn't care less about my former supervisors reputation and no matter what anyone says, knows, thinks etc, no-one and nothing will stop me from starting another PhD, if and when I choose to do so! :) I started my PhD without knowing what I was letting myself in for. I chose a poor supervisor and paid the price. Now I know better, feel much more confident and will not settle for 2nd best.

You need to learn to bite your lip in these situations ...

(a) the concern isn't you trying to avoid your supervisor, but with this attitude would your supervisor really want to help you for the remainder of your PhD?
(b) you aren't going to get very far in academia (or any industry) with this approach
(c) what was the problem? ok, I'd be slightly peeved that I wasn't going but if you really wanted to (i) you could have arranged this yourself, (ii) you have done other conferences ... and ultimately shouldn't you be more concerned about finishing your PhD???!!!

just testing. (5 years old thread, shouldn't it be locked?)