Within the context of property rights systems, developed either by traditional tribal communities or by modern political communities, one will always be confronted with the problem of non-appropriated and abandoned assets. In the legal tradition, we use to call the first category res nullius, the second res derelictae. The question arises by which rule or procedure res nullius and derelictae should be brought under an ordered property rights regime and be put, provided transferability of such assets is recommendable, within the market circulation. This entry summarizes the modern economic theories on these issues.
Keywords: First Appropriation, Capture, Occupation, Auction, Title, Initial Acquisition