In some sense this question follows the question:
Is it necessary to obtain permissions for copying figures from published articles in your proposal/dissertation?
F'x's advice and my own university's very stringent requirements, I have applied for permissions for reuse of figures in my dissertation. I plan to drop the figures, the permission for reuse of which has not been provided freely by the respective holder.
I hadn't given this much thought before, but what permissions are necessary for reuse of figures in a dissertation defense? I mean the powerpoint presentation slides. Of course, clear and prominent attribution is the minimum requirement, but is there a clear law on this? It's become reasonably convenient to obtain permissions from US publishers (copyright.com), but what if the publisher in question is based in Europe?