You should read The Ethics of Liberty by Murray Rothbard.
http://mises.org/rothbard/ethics/ethics.asp
The way I see it, a “right” is a legal concept that’s distinct from a privilege. Unlike a privilege, a right is fundamentally inalienable and inherent by definition, while privileges are granted at somebody’s pleasure - somebody who holds a right over the dispensation of such a privilege. Rights are “God-given”, if you believe in God or enjoy the metaphor, and naturally emergent vis-a-vis the maximisation of utility if you don’t. I believe the distinction between utilitarian arguments for liberty and ‘natural rights’ arguments is unimportant and technical. I think the main reason Rothbard used the framework of a natural rights argument was to emphasise that whatever truly maximises utility would have to be naturally emergent, and not planned by someone on behalf of everyone else.
“Rights” which are written down in a constitution or bill of rights, for example, are really misnomers. They are privileges granted by the state authority that has the power to effect, interpret, change or repeal the constitution, thereby witholding the privilege it had granted to its subjects.
The only right which can truly be regarded as inherent and inalienable - and therefore properly named - is a property right. An ‘owner’ is the only legal entity that exercises unfettered discretion over the use and disposal of a thing. He can grant privileges to others to use the thing in certain ways - to lease or lend it - but he can set the terms of lease and revoke such a privilege more-or-less at his own discretion, perhaps subject to self-imposed procedural limitations.
If it is the state authority which grants us privileges in their constitutions and legislation, then it means that the secular state is presuming the ultimate natural right of ownership over us, and merely leasing us the more-or-less free use of ourselves in exchange for abiding by its terms.
How could it possibly be that an alien and fundamentally fictional entity like the state has a superior claim to initial acquisition of ownership over a person than the person themself? Is it the state that learns how to walk and talk and work on behalf of a person? Essentially, self-ownership is taken as axiomatic, because it is absurd for a person to lease himself from an absentee, fictional alien entity from the moment he comes into the universe.
The non-aggression principle is thereby deduced as the appropriate ethical starting-point, if all persons are equal insofar, and no further, than they have equally valid claims of absolute sovereign ownership over themselves.
The acquisition of property beyond one’s self is, therefore, ethically appropriate insofar as it does not violate the non-aggression principle. Initial acquisition of ownership is only possible where something was genuinely unowned or abandoned, and transfer of ownership is only possible if it is voluntary.