I believe in a private contractural system that is negotiated between all the parties who voluntarily become party to it. The base contract would cover things such as property rights, torts, and other societal norms and provide a mechanism for resolving disputes through third-party arbitration. It would function like a constitution but be completely opt-in and and voluntary to leave.
This is a monumental task, and a work in progress, but I believe it can be done.