Unfortunately, you cannot play all DVDs in Ubuntu out of the box. Some packages need to be installed manually due to legal issues in some countries.
If you find yourself getting errors like VLC is unable to open the MRL, chances are this is your problem. It’s a simple fix (paste this into a terminal/console):
sudo wget –output-document=/etc/apt/sources.list.d/medibuntu.list http://www.medibuntu.org/sources.list.d/$(lsb_release -cs).list && sudo apt-get –quiet update && sudo apt-get –yes –quiet –allow-unauthenticated install medibuntu-keyring && sudo apt-get –quiet update && sudo apt-get install libdvdcss2 ubuntu-restricted-extras;
This will add the medibuntu packages to the repository and install the stuff you need to play DVDs, including encrypted ones.