From reading libertarianism, my understanding is that you must own your will in order to own your body. Also, my understanding is that people own their actions, for example, they own their labor, and they also own bad things they committed like the act of murdering and stealing.
Perhaps it’s more accurate to say that the will is the faculty by which a person exercises ownership over his mind and body. Ownership is controlling the use of means. Means are items used in action, not action itself. Action is applying means to attain ends.
Take a look at Murray Rothbard’s book, The Ethics of Liberty.