How do you block Ireland from buying

Sorry if this has been asked and answered before, every sale from the Republic of Ireland has ended up being returned to sender after being refused by customs, all correct information has been added to the label and custom form via click and drop, we ship internationally all the time only Amazon orders come back. We have blocked all other EU countries for this reason and many others due to customer returns and custom charges. We also had a sale from Malta, no other choice but to send it! Help please TIA