EagleJCS nailed it. Whether or not the BSA rules fit our agenda for wearing kilts, he has it right.

Although I'm not currently registered, I have a long history of BSA leadership on the unit, district and council levels. As a Woodbadger (used to be an Eagle -- and a course director, too) I have the opportunity to be an Honorary Members of the Clan MacLaren Society. Not being currently registered, I'm not entitled to wear the Scout uniform. If I have the opportunity to attend one of my grandson's Scouting events, I would consider wearing a MacLaren tartan kilt as civilian attire, but not as part of a Scout uniform as a registered Scouter.