Any moral ethic worth examining must be universal. That is if something is right or wrong for me, it must also be right or wrong for you. This is a system of ethics that applies universally to all individuals regardless of culture, nationality, race, sex, religion, sexual orientation, wealth, or any other distinguishing feature. Otherwise, we would have difficulty judging human action.
The law itself was originally created in order to protect property. However, the law has been falsely attributed to being the reason property exists in the first place. At least, this is what the state would have us believe. The law does not create property rights because these already existed before the law was created. It is this false attribution that allows the state apparatus to conduct its mission of expropriation.
It must be noted that the non-aggression alone can never be the starting point in justifying moral behavior or serving as a fundamental principle of ethics. There must be a justification of the non-aggression principle before such a case can be made. The very implication of the term “principle” implies that non-aggression serves as the foundation for a system of ethics, which it cannot be. It is certainly not an axiom since it is not a self-evident truth.
To make a claim of ownership implies a claim against others. That is, others must refrain from interfering with your use of that thing. As such the very act of the body occupying its standing room is to make a claim against others because only one body can occupy the space at a time.