Well, there it is in black and white - Scotland has no firm legal claim on Shetland. But as long as the population keep liking cats on Facebook, picking their lottery numbers and dressing up as Vikings they're stuffed. Lack of action will lead to a future Government maybe letting us have it back when the oil and fish have run out... An excellent, ground-breaking, well researched book. READ IT SHETLAND.
Although it deal with a legal non-issue due to the fact no other nation has claims on Shetland. The difference between feudal and udal property laws doesn't play a role in the matter although it would solve the question of who the people would be in a so-called people's sovereignty:
Is it an interesting read on the legal history of Shetland.