Rechtsstaat (German: Rechtsstaat) is a doctrine in continental European legal thinking, originally borrowed from German jurisprudence, which can be translated as a "legal state", "state of law", "state of justice", "state of rights" or "state based on justice and integrity". It is a "constitutional state" in which the exercise of governmental power is constrained by the law, and is often tied to the Anglo-American concept of the rule of law, but differs from it in that it also places an emphasis on what is just (i.e. a concept of moral rightness based on ethics, rationality, law, natural law, religion or equity). Thus it is the opposite of Obrigkeitsstaat (a state based on the arbitrary use of power).
In a Rechtsstaat, the power of the state is limited in order to protect citizens from the arbitrary exercise of authority. In a Rechtsstaat the citizens share legally-based civil liberties and they can use the courts. A country cannot be a liberal democracy without first being a Rechtsstaat.
German writers usually place Immanuel Kant's theories at the beginning of their accounts of the movement toward the Rechtsstaat. The Rechtsstaat in the meaning of "constitutional state" was introduced in the latest works of the German philosopher Immanuel Kant (1724–1804) after US and French constitutions were adopted in the late 18th century. Kant’s approach is based on the supremacy of a country’s written constitution. This supremacy must create guarantees for implementation of his central idea: a permanent peaceful life as a basic condition for the happiness of its people and their prosperity. Kant proposed that constitutionalism and constitutional government ought to be sufficient to guarantee this happiness. Kant had thus formulated the main problem of constitutionalism: "The constitution of a state is eventually based on the morals of its citizens, which, in its turn, is based on the goodness of this constitution."
"Kant's political teaching may be summarized in a phrase: republican government and international organization. In more characteristically Kantian terms, it is doctrine of the state based upon the law (Rechtsstaat) and of eternal peace. Indeed, in each of these formulations, both terms express the same idea: that of legal constitution or of "peace through law." ... Taking simply by itself, Kant's political philosophy, being essentially a legal doctrine, rejects by definition the opposition between moral education and the play of passions as alternate foundations for social life. The state is defined as the union of men under law. The state rightly so called is constituted by laws which are necessary a priori because they flow from the very concept of law. A regime can be judged by no other criteria nor be assigned any orher functions, than those proper to the lawful order as such." 
The expression Rechtsstaat can be found as early as 1798, but was popularised by Robert von Mohl's book Die deutsche Polizeiwissenschaft nach den Grundsätzen des Rechtsstaates ("German Policy Science according to the Principles of the Constitutional State") (1832–1833). Von Mohl contrasted government through policy with government, in a Kantian spirit, under general rules.
The most important principles of the Rechtsstaat
The most important principles of the Rechtsstaat are:
- The state based on the supremacy of national constitution and exercises coercion and guarantees the safety and constitutional rights of its citizens
- Civil society is equal partner to the state (the Constitution of the Republic of Lithuania describes the Lithuanian nation as "striving for an open, just, and harmonious civil society and State under the rule of law (Legal State)") 
- Separation of powers, with the executive, legislative and judicative branches of government limiting each other's power and providing for checks and balances
- The judicature and the executive are bound by law (not acting against the law), and the legislature is bound by constitutional principles
- Both the legislature and democracy itself are bound by elementary constitutional rights and principles
- Transparency of state acts and the requirement of providing a reason for all state acts
- Review of state decisions and state acts by independent organs, including an appeal process
- Hierarchy of laws, requirement of clarity and definiteness
- Reliability of state actions, protection of past dispositions made in good faith against later state actions, prohibition of retroactivity
- Principle of the proportionality of state action
- Monopoly of the legitimate use of force (sometimes amended to "monopoly on/of the legitimate initiation of force" or "monopoly on/of the legitimate use of aggressive force" in states that operate under an agency-contract [Lockean] rather than alienation-contract [Hobbesian] theory of legitimacy, such that individuals retain the right to take the actions that they also authorize the government to perform on their behalf)
Russian model of Rechtsstaat – a concept of the legal state
The Russian legal system, born out of transformations in the 19th century under the reforms of Emperor Alexander II, is based primarily upon the German legal tradition. It was from here that Russia borrowed a doctrine of Rechtsstaat, which literally translates as legal state. The concept of “legal state” (Russian: Правовое государство, pravovoe gosudarstvo) is a fundamental (but undefined) principle that appears in the very first dispositive provision of Russia’s post-Communist constitution: "The Russian Federation – Russia – constitutes a democratic federative legal state with a republican form of governance." Similarly, the very first dispositive provision of Ukraine’s Constitution declares: "Ukraine is a sovereign and independent, democratic, social, legal state." The effort to give meaning to the expression "legal state" is anything but theoretical.
Valery Zorkin, President of the Constitutional Court of Russia, wrote in 2003:
- Becoming a legal state has long been our ultimate goal, and we have certainly made serious progress in this direction over the past several years. However, no one can say now that we have reached this destination. Such a legal state simply cannot exist without a lawful and just society. Here, as in no other sphere of our life, the state reflects the level of maturity reached by society.
The Russian concept of legal state adopted many elements of constitutional economics. Constitutional economics is a field of economics and constitutionalism which describes and analyzes the specific interrelationships between constitutional issues and functioning of the economy including budget process. The term “constitutional economics” was used by American economist – James M. Buchanan – as a name for a new academic sub-discipline that in 1986 brought him the Nobel Prize in Economic Sciences for his “development of the contractual and constitutional bases for the theory of economic and political decision-making.” According to Buchanan the ethic of constitutionalism is a key for constitutional order and "may be called the idealized Kantian world" where the individual "who is making the ordering, along with substancially all of his fellows, adopts the moral law as a general rule for behaviour". Buchanan rejects “any organic conception of the state as superior in wisdom, to the individuals who are its members.” Buchanan believes that a constitution, intended for use by at least several generations of citizens, must be able to adjust itself for pragmatic economic decisions and to balance interests of the state and society against those of individuals and their constitutional rights to personal freedom and private happiness. The standards of constitutional economics when used during annual budget planning, as well as the latter's transparency to the civil society, are of the primary guiding importance to the implementation of the rule of law. Also, the availability of an effective court system, to be used by the civil society in situations of unfair government spending and executive impoundment of any previously authorized appropriations, becomes a key element for the success of any influential civil society. Some Russian researchers are supporting an idea that, in the 21st century, the concept of the legal state has become not only a legal but also an economic concept – at least for Russia and many other transitional and developing countries.
- Civil society
- Constitutional economics
- Immanuel Kant
- Legal doctrine
- Philosophy of law
- Political philosophy of Immanuel Kant
- Nuremberg Principles
- Rule According to Higher Law
- Rule of law
- State (polity)
- Carl Schmitt, The Concept of the Political, ch. 7; Crisis of Parliamentary Democracy
- Friedrich Hayek, The Constitution of Liberty.
- History of Political Philosophy, edited by Leo Strauss and Joseph Cropsey, The University of Chicago Press, 1987, pp.581-582,603
- Luc Hueschling, État de droit, Rechtsstaat, Rule of Law (Paris, Dalloz, 2002), pp 36-40. In this context Polizei means "policy", not "police": Stewart, 2007.
- Klaus Stern, Das Staatsrecht der Bundesrepublik Deutschland, I 2nd edition, § 20, Munich 1984, ISBN 3-406-09372-8; Reinhold Zippelius, Allgemeine Staatslehre/Politikwissenschaft, 16th edition, §§ 8 II, 30-34, Munich 2010, ISBN 978-3-406-60342-6
- Constitution of the Republic of Lithuania, as amended, 2008
- The World Rule of Law Movement and Russian Legal Reform, ed. Francis Neate and Holly Nielsen, Justitsinform, Moscow (2007).
- James Buchanan, The Logical Foundations of Constitutional Liberty, Volume 1, Liberty Fund, Indianapolis, 1999, p. 314
- Buchanan Entry at Nobel site
- Peter Barenboim, Natalya Merkulova. "The 25th Anniversary of Constitutional Economics: The Russian Model and Legal Reform in Russia, in The World Rule of Law Movement and Russian Legal Reform", edited by Francis Neate and Holly Nielsen, Justitsinform, Moscow (2007).
- Daniel R. Ernst – Ernst Freund, Felix Frankfurter and the American Rechtsstaat: A Transatlantic Shipwreck, 1894–1932. Georgetown Law Faculty Publications, October, 2009.
- Matthias Koetter, Rechtsstaat and Rechtsstaatlichkeit in Germany (2010), Understandings of the Rule of Law in Various Legal Orders of the World, Wikis of the Free University Berlin, edited by Matthias Koetter and Folke Schuppert
- Iain Stewart, "From 'Rule of Law' to 'Legal State': a Time of Reincarnation?" (2007)
- A. Anthony Smith: Kant’s Political Philosophy: Rechtsstaat or Council Democracy? University of Notre Dame du Lac - 1985