If you are in the fanclub and hit for Kokuritsu, instructions came on the orange sheet with your tickets (on the inside top right corner). The orange sheet gave a URL to register for a special Kokuritsu concert email mailing list to give updates on the weather forecasts or any emergencies regarding the venue.
However, the fanclub stated today that the "mailing list" will also serve as a means to crack down on ticket resales. Basically, unless you can login to J-net under your own fanclub name and register your own ticket serial numbers with that URL on the orange sheet (it also requests that you register the membership information of any guests you are bringing with you if they are fanclub members)... Well, I'm not saying they'll be able check the identities of everyone at Kokuritsu upon entrance due to time constraints (highly doubtful), but if you do not register your tickets, I would expect the chances of staff going to those seats and doing random ID checks are much, much higher.
So if you are a fanclub member and played by the rules getting your tickets, please be 100% sure this time to bring your fanclub membership card because the chances of it being required for entrance have now increased exponentially. Photo ID with your fanclub-registered address is also recommended just as a precaution. If you did not hit for tickets yourself, but are going with someone else who did, I recommend you be sure to tell them about this so they can register for both of you.
If you bought your tickets from auctions, or off ticket.co.jp, there's a very good chance you're SOL, depending on how organized JE is about checking.
I would guess you can expect to see similar tactics being used for every venue in the future as well. Dome results are coming out now, so if you were planning to buy from a scalper, you probably will want to rethink that.
Also, a very large number of people auctioning on Y!A who provided photos of their tickets took care to cover up their names, fanclub numbers, and seats...but neglected to cover up the tinier serial number at the bottom, and they can track you just as easily with that. People have been reporting those serial numbers to JE liek whoa this time. If you bought from such a person, I think it is fairly safe to say that you are getting kicked out if they find you.
(EDIT: I know people are commenting it's impossible to check everyone's info, and I agree at a venue that big. Checking ID at the entrance would be way chaotic. But auctions, even if they hide all the information, say "the ticket is in the range of seat numbers 30~50" or whatever. If a significant number of the FC members in those twenty seats registered their seats, and that auction was reported to the fanclub... If I were JE staff, I'd probably do random ID checks among the people in that row who didn't register. Now, it may end up that nothing happens at all because the staff just has better things to do, or JE just won't have their shit together enough to implement this to any great effect. But that's how I'd do it.
I'm also seeing random speculation that rather than just using the registry list as a tool to bust people, they may be making notes of the people who register their seats as the well-behaved fans who follow the rules, and give those fans some edge in future ticketing lotteries. It's totally baseless speculation, but either way I don't think it can do any harm in registering to let JE know you play nice.)