I think videolan repos has libdvdcss2. Having typed that, there are a few ways you can do this with repos (probably more) .... for example:
a. add videolan to your repos (and not packman);
b. add packman to your repos (and not videolan);
c. add both packman and video lan to your repos.

I prefer option-b, as I like packman more than videolan, and sometimes videolan and packman rpms have conflicts with each other. Others prefer option-a (liking videolan more than packman, and want to avoid the videolan-packman conflicts), and some prefer option-c and those users (who prefer option-c) are willing to put up with the occasional conflict between packman and videolan.

In my case, since I use packman in my repos (and not videolan), and since packman does not have libdvdcss2, I install libdvdcss2 with the following command (distribution version independant):
entering root password when prompted.