You contract (that is, pay for directly) for those protection services, perhaps including apprehension of criminals (bounty hunting, anyone?) that you are unable or unwilling to provide for yourself. You do this with a willing provider for a sum of compensation that is mutually agreeable to both you, under terms of mutual consent (a
'Contract'). If you choose to engage in such a contract with others with whom you have formed a partnership (another form of contract) you are certainly free to do so.
As opposed to the system we have in place now where you neither have a choice in how much you pay nor in what services you have a right to expect.
Point being, the obligation to provide such services, in the end, rests with YOU.