Amidst Anarchocapitalist authors such as Murray Rothbard, are there any who discuss the possibility of privately-owned countries, with their own set of private laws, police services and courts?
Murray Rothbard gave a "natural rights" justification for an AnCap society.
David Friedman (son of Milton Friedman) discusses and gives a consequentialist defence for an Anarcho-Capitalist society. It's discussed in his book 'The Machinery of Freedom' and references 14th century Iceland for an approximation of how a society based on private laws and courts work.
Murray Rothbard, however, is still is the best known AnCap theoretician.