If they do, though, it's high time to check if these additional clauses are honored.
This was based in ideas trying to explain what property is, why one person was rights to it and another doesn't. A wild forest is not property. A farm is. Hence labour, habitation, productive use etc. make something property. It's the kind of philosophy that gets very theological, with precise definitions and arguments between theorists that seem very arcane an pointless in retrospect.
I'm not promoting the theory. It just seemed relevant in the context of a liberal/libertarian quip. These ideas are foundational to ideas of private property, later economic freedom etc. It's part of the history of ideas related to right leaning politics today.
In practice, I'm not sue if this is workable. But if it is, I don't think an abstract sanctity of private property is necessarily a barrier. That unused property makes fro a weaker claim is justifiable by common sensibilities, right or left wing philosophy.
They might class perpetually vacant properties as abandoned and therefore returned to the common. When New world land was doled out in square mile allotments (The US, Australia..), improving the land was a prerequisite to your claim. This is often thought of historically as a deal: 'you improve this land and we'll give it to you.' But the justifications at the time was more philosophical: you improve this land and you own it, by definition.'