Buchanan believes that the modern government operates between the Leviathan model and the democracy model, and the role of the Democratic restriction mechanism trusted by the public is increasingly weak. Therefore, a new form of political technology and democracy is required to control the spread of bureaucracy. Hence, Buchanan proposed to put “constitutionalism” before “democracy” and combine “rule restriction” with “non-rule restriction” to realize his constitutional proposition. Buchanan’s constitutional economics is composed of methodological individualism, contractualism and the principle of consensus. This paradigm has standardized and renovated the existing theories of law and politics.