Are GS1 codes the only globally verified and certified product codes?
There are companies that sell individual barcodes or GTINs (or EAN codes). This may seem like a good deal, but only GS1 can offer you all the benefits of official product codes. GS1 is also the one and only issuer of standardised GTINs and barcodes worldwide, so you can sell your products anywhere you want. If you use unofficial barcodes, and this causes problems later on (e.g. because it turns out that the code is not unique), GS1 won’t be able to help you.
So beware of "pirate" barcode resellers!