The possible exception I can think of is this.

Clan loyalty was not just by blood or fathers surname. Anyone could pledge loyalty to a clan by taking an oath and agreeing to serve the chief and clan when called upon.

So theoretically Joe Wu the poor shipwrecked Chinese sailor finding himself being cared for by Highland Chieftain Dave could pledge loyalty to that Clan and be authorized to wear the Tartan.

Even today a letter to a Standing Clan Chieftain requesting to wear his Tartan is usually met with a wonderful and thankful permission to do so.

Now I'll throw a wrench into this question. If you feel you would only be comfortable wearing a Tartan you have a feeling for, how would you feel about wearing a district, State, or fashion Tartan?