Yes you can, but it's not the best. First of all, weed ashes are much finer, so you need to put a screen at the bottom of the pipe or you get ashes in your mouth. Secondly, the bowl of a regular pipe is way too big. You just want to put a -pinch- of pot in a pipe.
I used to smoke a pipe and there were pipes with very small bowls--that would be best.