I have somewhere a copy of a book called The Border Ballads, written by J Reed or Read. It is not to hand, so I apologise for the shaky nature of what follows.

There was a border area of no-mans-land between Scotland and England, which was difficult to govern, due to uncertainties as to whose laws applied. There were, however, certain laws applied to those who lived there as attempts to combat those who lived like bandits. These included rules about fortifying dwellings, and lighting beacons when marauders were marauding. I feel certain that, given the circumstances in the song, the events relate to a border lord whose keep was not adequately fortified, and had to do something about it to comply with the recently-issued edict. A little more research could provide a very close date for the song, as the laws mentioned are quoted in the above book.