How cancel an order, in which buyer order an item, from a State I m not send.

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Hi, I stated to a listing that I m not deliver to few States, more States than  , US Protectorates, Alaska/Hawaii, APO/FPO, PO Box. What I have to do? I have already sent a message to the buyer, and ask her to cancel the order. 

But I think that I have to cancel the order . What reason I have to ask for cancel the purchase?