Gravity is universal. Even if you don't like it, or rail against it, gravity is going to win, because its universal. No matter if you acknowledge it or not, its there, yanking you around.
However, you claim to have a universal right to your own body as your personal property.
If I were to dump you in Ancient Rome amongst a bunch of Gauls about to be captured by Caesar, and you were enslaved (and since you likely don't speak a local language, you'd end up at best a menial laborer), you would no longer have that right to your person.
They can take that so-called "universal" right away from you. Beat you, break you, or kill you. Your right doesn't act to trump their ability, therefore its not a universal right that always exists. Mcbry is correct: There are no rights except those enforced by power, be that direct power, cultural power(that would be why we don't have slavery now... its literally unthinkable for the great mass of people in Western Civilization), or the like. Property rights are given by society in some form, they don't exist outside of it.
For somebody who seems to be a fairly solid realist, you're wandering off into happy fuzzy bunny land a bit here, Ghost. :)