There have been numerous complaints about 0 point earning guilds appearing in GW Brackets, and yet the Devs have stated that someone in the guild is registering them for the next war.
Taransworld only tracks the GW results for PC/Mobile, but even as recently as last war there was a Guild in b8 that scored 0 points. While if you search in previous wars from lowest score to highest, you will notice some guilds scoring 0 points in consecutive wars.
If registration is indeed automatic, then that should be fixed as well. But I do not believe it is. One of our current members was in an opposing guild that failed to register a few months back, and missed the following GW. It has since disbanded (The Dreadnoks). Better for us, he is now one of our Vanguard.