Private property is a monopoly on the use of natural resources granted by law and enforced by the threat of physical harm. As soon as you admit the possibility of competition for natural resources you have introduced law, and at that point the only question is who shall enforce the law and for whose benefit. There is no answer to that question that is provably correct, but so far "states, for the benefit of their political constituency" has been the answer that has overwhelmingly outcompeted all others, and the vast majority of effective political disagreement in the modern era is between statists regarding exactly how a state's political constituency should be defined and how best to benefit it.