We subsist under the law where we claim our rights and are obliged to do something enforced. What is a law? The question would be perplexing in history, and one of crucial themes with many lawyers or legal philosophers. As we know, two most important perspectives had earned a universal and historical forge in academics, to say, the natural law and legal positivism. The concept of natural law deals in its primacy for the humanity and natural order which often can be traded as something inviolable or inalienable. The concept has strands in several aspects; (i) its anchor with the civil democratic revolution around 17 and 18 centuries (ii) its supremacy with the new constitutional states (iii) less quality as a realist law from ambiguities and lack of clear definition. The concept of public policy may be related with the social justice, ethics and administration. It generally pursues a justice and desired state of public or community where the tension and conflict always exist between the ruling class and citizens. Historically, the public policy could be mightier to address the society than law where the benevolent Kings or Sovereigns liked to address both their needs and social justice. They may abrogate, more in endowment and divinity, the laws or social customs. The tension between the public power and private interests could be one reason as well as offers a good dualism in understanding the rule of law concept and advent of modern democracy. In this dimension, the King would no longer be divine nor entitled to exercise a plenary power of state rule. Instead, the popular sovereignty in the US democracy or parliamentary type in the UK were to be established to resolve a feudal conflict within the class and society. Lighted to be in vein of influence could arise the two contexts which are a contractarian view and plutocracy desire of the founding fathers. They underlay the mood and philosophical ethos of US revolution. Hence, three concepts as a pillar in private law were sanctified in the very foundation of US constitutional state, sanctity of property right, freedom of contract and due limits for the civil liability. The governmental power should be limited to protect the life and limb of citizens which addressed the Hobbes’ evil, “war against all the rest.” The due process concept was expressed as a fundamental principle of constitution where the human rights are inviolable and inalienable. The separation of powers principle could serve the freedom and wealth of new civil class in the continent, and bicameralism was devised for the check and balance within the federal congress. They see the role of judicial branch is important to preserve their civil interest. Then we can derive some assumptions between the law and public policy. First, a law plays to protect the private interest while the public policy pursues the social justice and mediates the competing interests, “private v. private” and “public v. private.” The civil courts may address a first nature of conflict and the law of takings or regulatory laws may deal with the second aspect. Second, the public or administrative law can shape a legal plane of bureaucracies or public administration, and may guarantee the rule of law ideals. It plays as an enabling authority and, on the other, monitors an arbitrariness and unfairness in the bureaucratic government. In this context, the unresponsive and unfathomable bureaucracy in the Kafka’s could be remedied. Third, for the welfare state in the late 19th and 20th century, a law can well be seen as one of authoritative expression of public policy to redress the evils of capitalist states. Some public laws, such as the Sherman Act classically and Lanham Act recently, may act to regulate the monopoly or oligopoly while other laws were enacted to restore justice between the labor and employers. Through the chapters, the fundamentals of law and public policy will be considered to address their proper status.