Property rights are determined by those able to mass sufficient violence it to define their constituency and their limits.
Under natural law property rights ARE absolute. It is the externalities that determine their limits not whether or not one has demonstrated investment in them.
Ergo, scientifically property rights must be absolute, contingent upon the consequences of their exercise.
Practically speaking property rights evolve to suit the median of the population, which is why western europeans prior to 1900 had the worlds highest degree of property rights.