And see Ayn Rand, "The Nature of Government":
The proper functions of a government fall into three broad categories, all of them involving the issues of physical force and the protection of men’s rights: the police, to protect men from criminals—the armed services, to protect men from foreign invaders—the law courts, to settle disputes among men according to objective laws.
These three categories involve many corollary and derivative issues—and their implementation in practice, in the form of specific legislation, is enormously complex. It belongs to the field of a special science: the philosophy of law. Many errors and many disagreements are possible in the field of implementation, but what is essential here is the principle to be implemented: the principle that the purpose of law and of government is the protection of individual rights.
Today, this principle is forgotten, ignored and evaded. The result is the present state of the world, with mankind’s retrogression to the lawlessness of absolutist tyranny, to the primitive savagery of rule by brute force.