Many of you said a right thing: Unlimited is Unlimited, cards cannot be banned.
We all know that US Slowking is broken, and Japanese version is not.
The most valuable solution, I think, is - as 1 of you proposed - to authorize a new format, different from Unlimited. A Restricted format, with some Ban as Sneasel, Slowking, and - why not - CPU Search, and so on.
PUI has the right to make rulings on the cards, they are now responsibles for this game, and for all formats. WoTC was able on that when cards were produced by them, but they can no longer make any more rulings on Slowking.
Neo-on is gone, the Ban is gone too.
Or PUI makes an Errata on Slowking (which is difficult as banning it was, but it's the best thing to do), or PUI leaves Slowking in all its brokeness in Unlimited. But where's fun? Yes there are many cards to counter the King, but if I want to make an Unlimited deck, why have I to cut out cards (and room) from my deck only to add the Slowking counters, as I know that 90% I'll find a Slowking in my opponent's arena?
We should suggest to make an Errata on the website, and on te Floor Rules too. And each and every Professor that runs an Unlimited tournament should advice players before the start that an errata was made.
Do you know how much time we (in Italy) had to spend to explain to players that the 2nd attack of Dark Ursaring was mis-translated in italian, so that it seemed to be the same Sneasel's Beat Up attack? Many of them made a Dark Ursaring deck, but - after explaining the real version of the card - they started to cry 'cause their deck were useless.
Maybe the same thing will happen with Slowking... but only at the start. After, all players will know about the errata and troubles will be out.
That's my .2 eurocents