People often get a bit mixed up over the Debateable Land. It wasn't what the Border Marches were called. The border was well defined enough apart from a small strip of land in the west around Canonbie. There was a quite small piece of territory only about 8 miles or so in length where the border was disputed and belonged officially to neither kingdom until it was settled in the mid 16thC. That was the Debateable Land. Just a tiny fraction of the West Marches both Scottish and English. The demarcation in the mid 16thC was created by the Scotch Dyke. Just a tiny fraction of the length of the border. Yes the riding names and broken men alike in the Borders were called Border Reivers but this song is about reiving in the Western Isles. Nothing to do with Border Reivers. Isn't it about McNeil of Barra?