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To my recollection, all Non-English cards are banned at events run in countries where English is the only official language used for the TCG. Events like worlds are an exception to this rule.
I could be wrong on that, though. Just going by memory and don't have access to the official rules at present.
Well, yeah. They're not very popular cards in the English speaking world because of the restrictions in place and because they're not the original language.
Also, Bulbapedia's article on it says they're not allowed, and I'm going to assume that's accurate enough since the cached results from the official Pokemon site on Google indicate the same thing.