You can find all the details here on the Clan Donald Canada forum.

The key, apparently, to a successful claim for duty-relief under section 9937.00.00 of the Canada Customs Tariff Schedule of 2005 is to stipulate, in writing, your qualifications under the section:

All I had to do was submit a letter in writing stating which Ethnic/Cultural group I belonged to, and the event at which I was to employ the goods to express my heritage: I used a public event, viz. the Glengarry Highland Games (Maxville, Ontario). Perhaps it would be slightly more complicated if I was brokering my own package; but, I have gotten rebates from CBSA before, and their bureaucracy does not seem to be overly obtuse. I imagine I would have achieved the same result dealing with them directly.