Yes you own the blu ray, but you don't actually own _the movie_. Despite owning the disc, your legal rights to how you can view the content on it are quite specific, and I believe that circumventing the DRM on it is illegal. So the fact that you have physical ownership of the disk is almost tangential to the discussion.

And of course there's always the whole, "Well actually the government has the final say in everything so does it count that you 'own' something if the government can simply take it away from you." but that's a whole other can of worms!