Wearing another clans Tartan?

[kilted scholar]

There is another aspect to this question that should be borne in mind.
The ultimate authority in determining what tartan is and should be associated with a particular clan is the clan chief.
There are often a number of tartans that are named after particular clans but are not recognized by some chiefs as tartans associated with that clan.
For example, Torquil, 13th Duke of Argyll, Chief of Clan Campbell, follows the practice of his father, the 12th Duke in recognizing "plain undifferentiated Campbell" as the only tartan for the clan. While Campbell of Breadalbane, Cawdor and Loudoun are acceptable for those branches, only plain Campbell receives his approval. In his estimation, there is no such thing as Hunting Campbell, Dress Campbell and Campbell Red.
So there may be a range of instances in which a tartan may be publicly available and named after a particular clan but may not necessarily be recognized by the chief as a tartan for that clan.