So, my codex just updated itself.
Interesting situation for a tournament organizer. These codex have rules changes that are getting rolled out over the course of a week or so. There is no announcement or changelog that describes which changes were made. So, you could put on an event, and after folks submit their lists, an update to the e-codex can come out, which invalidates their lists.
Some people who show up will simply have a different version of their rules than other people, and there will be no way for anyone who hasn't gotten the update yet to even know that another version of the rules exists at all. Furthermore, if you HAVE gotten an update, there will be no way to look at what the rules WERE at any point in the past, so, for example, you wouldn't be able to say "for this event we're using the version of the rules as of January 25th" - after people's e-codexes update, they no longer have any way to know what those rules were (other than their own memories).
Also, depending on whose e-codex you look at to investigate a question, you'll get a different answer (depending on whether the person was an early recipient of phased update rollout or not).
Interesting times, eh?