According to the national legal and regulatory provisions on customs and VAT, all non-EU citizens have the right to apply for a VAT refund, for the goods purchased within Italian territory.
The tax regulations currently in force defines that Customs Office is the only one authorized to stamp tax documents to be used by non-EU citizens for VAT refunds.
A tax document (invoice or receipt) stamped by Italian Consulates or Embassies would therefore have no value in regard to a VAT refund and the retailer will not process any refund against receipt of such an invalid document since in case of any control (by the Italian Finance Police or the Revenue Agency) sanctions would be applicable.