Property Rights

From the notes posted from Rizzo's lecture, I believe Property Rights is a moral enduing system that is based upon others payment for ownership. It's understandable to note that if someone is making a payment for said set of land that they should do anything with hat set of land that will not conflict with illegal activities. It is also understandable that you have the right to remove those who are on your land or disobey the orders placed on that set of land because it is obviously yours. Private property falls into that category. But I also believe it is based on a moral system throughout society. For example, kids would not try to play on people's lawns because they know that the owner would have them get in trouble no matter how much fun they are having. But what I was also thinking about was when someone decides to put their stuff on a chair beside them to save the space for their friends. Their friend did not pay for the chair so why do we feel the need to find another seat when such predicament comes? What if you leave your own bag to try to do something and end up coming back to the seat being taken away? Based on property rights, is it wrong to take the seat or is it wrong to move the bag? If moving the bag is violating private property, is the seat also an extension of the private property?