A tartan among us

[Mike_Oettle]

Corbmonster, since you have made your selection, this is probably redundant, but since you asked: “Am I safe in assuming heritage of Scotland, and Scottish national are universal?” I thought I would venture a reply.
The simple answer is that if a tartan is specifically for a clan, for a military unit or for some other corporate, you are not really supposed to wear it unless you belong. (Since there are no kilt police, you could go ahead and wear it anyway, but that is not answering your question.)
But a great many tartans, particularly those with the word Scotland in their name, are fashion setts, not owned by any such organisation. (The exception is the one simply called Scotland, which is a family tartan.) This means that Spirit of Scotland, Scotland’s Heritage or even Scottish National are available for anyone to wear. (So far, at any rate, Scottish National has not been adopted by the Scottish Parliament or any other official body.)
While Black Watch is associated with the Royal Regiment of Scotland, and with the Canadian regiment affiliated to it, it is a universal tartan. But even in its military use, it has been worn by other regiments (notably the Argyll and Sutherland Highlanders in both Scotland and Canada). The Argylls wear it in muted shades (unlike the harsh modern dark blue and dark green of Black Watch regimental), and the muted version is also officially the tartan of Clan Campbell, as well as the hunting tartan of about half a dozen other clans.
For this reason many folk who are not associated with one of the regiments or clans mentioned prefer to avoid it. But it is nonetheless acknowledged as a universal tartan, as is Royal Stewart, which has traditionally been regarded as the property of the British sovereign. Royal Stewart is also worn by military pipe bands with specific royal associations. But civilian pipe bands with no royal connections also wear it, as do many ordinary folk, whether they have it in kilt form or some other format.
There are several other tartans that are either generally regarded as universal, or have been specified as such by their designers. But I would not recommend all of them to people wanting a universal tartan.
I have just overheard a colleague saying: “You’ve got to know the rules before you can break them.” He was not talking of kilts or tartans, but it’s a principle to go by with regard to tartan, too.
Regards,
Mike