It may give him an unfair advantage or alter play in a fashion you find disagreeable. If you chose to act as did the individuals in the above examples, you could call upon an adult or an older sibling to force the child to share his ball or his game and to play by your rules. On the other hand, you could attempt to persuade him to return to the rules you traditionally play by. You might try to shame him into behaving less childishly. I'll go find someone else to play with.
Property rights provide the means for implementing the right to one's life.
You must be free to use your property in any manner you want so long as you do not endanger the life or property of someone else. Property rights help delineate the proper boundary between one person and another. They help us recognize those aspects of the world which are subject to our control and which are under the authority of others. Property rights help ensure peaceful interactions among individuals. Without them, only chaos and ceaseless conflict can result.