My apologies, I see what you're saying now CMcG.

Taking whiskey as an example, it needs to be distilled in Scotland to be 'Scotch Whisky', or distilled in Ireland to be 'Irish Whisky'

So maybe there should be an Irish Tartan Registry, which I guess would be a lot smaller.

Although what would happen to tartans with no historical basis? E.g American/Canadian ones, or more recent ones made here?
In a previous post I mentioned football club or university tartans which are very recently designed. Should these still be allowed on the Scottish Tartan Registry?