This is an issue with the encryption. In some countries it is not allowed to distribute this. But it is easily solved. The easiest way is to use mate-terminal.
If you want all restricted codecs just install ubuntu-restricted-extras
sudo apt-get install ubuntu-restricted-extras
If you just want to play the encrypted DVD’s just install libdvdread4, but then you have to issue a following command, so the do the following (also in a terminal)
sudo apt-get install libdvdread4
sudo /usr/share/doc/libdvdread4/install-css.sh
Hope it helps