I could ask several questions about this subject, but it could get quite complicated.
Instead, I will just raise this:
Why is a removable, sticky label regarded as a trademark denoting proof of manufacture in Murano? What happens to the original, genuine article that loses its label - does it suddenly become "unproven as made in Murano"? Why not use a form of trademark that could be added as a part of the actual glass item.
For info, here is a webpage (translated to English) and headed "veneto internet" that apparently gives details of the "legislatura".