The Criminal Legality Principle in 5 Questions

The Criminal Legality Principle in 5 Questions. The principle of legality in crime and punishment (legalite prensibi) is considered the “Magna Carta” of modern criminal law. This principle serves as the primary shield protecting the fundamental rights and freedoms of the individual against the potential misuse and arbitrariness of the state’s punitive power. As the most concrete reflection of the rule of law ideal in the field of criminal law, legality compels the state to declare in advance, with indisputable clarity, which actions it prohibits and what sanctions those who violate these prohibitions will face. This report aims to provide a layered analysis of the principle of legality in crime and punishment—from its philosophical roots and historical development to its constitutional and legal foundations in positive law, its sub-guarantees, and finally, its current reflections in national and international high court precedents—through five basic questions.

1- What Does “No Crime, No Punishment Without Law” (Nullum Crimen Sine Lege) Mean, and What Are Its Philosophical Foundations?

“No crime, no punishment without law” is the most well-known expression of the principle of legality. This principle is the fundamental axiom upon which modern criminal law is built.

A. The Comprehensive Definition of the Principle and Its Modern Formulation

In its most basic sense, the principle of legality means that which acts are considered crimes must be regulated in advance by law, and the types of sanctions (penalties or security measures) that will be faced by those who commit these crimes must also be determined in advance by law. This principle consists of two inseparable fundamental components:

Nullum crimen sine lege (No crime without law): An act cannot be considered a crime, and no sanction can be applied to the perpetrator, unless that act is clearly and distinctly defined as a crime by a law.
Nulla poena sine lege (No punishment without law): The penalty or security measure to be applied for a crime must also be predetermined by law in terms of its nature and quantity.

This principle was introduced into modern criminal law by the German jurist Paul Johann Anselm von Feuerbach. In his 1801 work, Feuerbach formulated the principle as “Nullum crimen, nulla poena sine praevia lege poenali” (No crime and no punishment without a prior penal law). Feuerbach’s theory links the principle not only to a matter of fairness but also to the prevention of crime (general prevention). According to his “psychological coercion” theory, for individuals to be deterred from committing crimes, they must know in advance which act is forbidden and what specific punishment will certainly result from violating that prohibition. Ambiguity eliminates this psychological deterrence.

B. Historical Background: A Reaction to Arbitrariness

The historical origins of the principle of legality did not reach the level of a serious “principle” until the 18th-century Age of Enlightenment. In Roman Law and the Common Law (Ius Commune) periods, it was common practice for judges to create law (judge-made law) in criminal proceedings and to punish crimes not found in the code through analogy. This led to serious problems such as “arbitrary judgments, disproportionality, and violence in punishments” that continued until the 18th century.

The principle of legality was born as a revolutionary philosophical and political demand against this judicial arbitrariness and unpredictability. The problem was not the absence of rules (legal vacuum), but the arbitraryinterpretation of existing rules or customs by judges, the application of disproportionate violence, and the arbitrary disregard for written law. Therefore, the demand of Enlightenment thinkers was not “more law,” but “more specific, predictable, and written law.”

C. Philosophical Foundations: Enlightenment, Social Contract, and Separation of Powers

The philosophical infrastructure of the principle was built by Enlightenment thinkers.

Montesquieu and the Separation of Powers: The political basis of the principle rests on Montesquieu’s theory of the separation of powers. According to this theory, the authority to define acts that disrupt social order as “crimes” and to determine “punishments” for them must belong solely to the legislative body, which represents the will of the people. The judiciary, on the other hand, should be “the mouth of the law” (la bouche de la loi), meaning it should be limited to applying the will predetermined by the lawmaker to the concrete case, not its own will. The principle of legality is the fundamental mechanism that establishes this separation of powers in the field of criminal law and prevents judicial activism.
Cesare Beccaria and the Social Contract: The individual-focused philosophical basis of the principle relies on the foundations laid by Cesare Beccaria in his 1764 work On Crimes and Punishments (Dei delitti e delle pene). According to Beccaria, people established the state through a “social contract” by renouncing some of their freedoms. However, this renunciation is not unlimited; people have transferred the minimum necessary freedom for the common good. The state’s power to punish is limited by this contract. In Beccaria’s words: “Only the laws can determine the punishments for crimes. The source of this authority is the legislator himself, who represents the entire society united by the social contract.” A judge imposing a punishment not foreseen by the law (outside the legislator’s will) is a violation of this social contract and a manifestation of arbitrariness (despotism).

D. Transition to Positive Law

These philosophical ideals began to transform into binding legal norms from the last quarter of the 18th century. The principle first appeared in positive law in the 1776 American Constitutions (e.g., decisions of the Philadelphia Congress). This was followed by the 1789 French Declaration of the Rights of Man and of the Citizen (Article 8). Subsequently, major codifications such as the 1787 Austrian Penal Code, the 1794 Prussian General Code, and the 1810 French Penal Code (Code Pénal) made the principle the foundation of European continental law. Its reflections in Turkish legal history can be traced through the Westernization movements, including the Tanzimat Edict, the Islahat Edict, and finally the 1876 Constitution (Kanun-u Esasi).

2- What Are the Constitutional and Legal Foundations of the Principle of Legality in Turkish Law?

The Turkish legal system has bound the principle of legality with strong guarantees at both the constitutional and statutory levels. The principle’s place in our legal system must be examined on the axis of the Constitution and the Turkish Penal Code (TCK).

A. The Constitutional Framework: The Pinnacle of Guarantee

The principle of legality is protected by multiple and interrelated articles in the Constitution. These articles form a “matrix of guarantees.”

Constitution Article 38 (Direct Basis): The place where the principle is directly and specificallyregulated is Article 38 of the Constitution.
- Article 38/1: “No one shall be punished for an act which did not constitute a criminal offence under the law in force at the time it was committed; no one shall be given a heavier penalty for an offence than the penalty prescribed by law for that offence at the time it was committed.”. This clause secures both the legality of the crime (Nullum Crimen) and the principle of non-retroactivity of unfavorable law(Lex Praevia).
- Article 38/3: “Penalties and security measures in lieu of penalties shall be prescribed only by law.”. This clause clearly guarantees the legality of punishment (Nulla Poena).
Constitution Article 2 (The Principle of the Rule of Law): This is the indirect but strongest philosophical and legal basis of the principle. Article 2 of the Constitution defines the Republic of Turkey as a “state governed by the rule of law.” The fundamental requirements of being a state governed by the rule of law are “legal certainty,” “specificity,” and “predictability.” As the Constitutional Court (AYM) has also emphasized, if a penal norm is not “specific and understandable,” and is “open to expansion by practitioners,” that norm does not materially possess the quality of “law” and thus directly violates the principle of the rule of law in Article 2 of the Constitution.
Constitution Article 13 (Limitation of Fundamental Rights): This article concerns which rights of the individual are affected by criminal law. Criminal law is, in essence, a regime of limitation on the most fundamental rights, such as personal liberty and security. Article 13 of the Constitution commands that fundamental rights and freedoms may be limited “only by law,” “without prejudice to their essence,” and in accordancewith the “principle of proportionality.” AYM and ECHR precedents accept that the concept of “law” here is not just formal (a text passed by parliament), but must also carry a material content (being specific, accessible, and predictable).

These three articles (38, 2, and 13) work together. When reviewing the constitutionality of a penal norm, it is not enough for that norm to merely comply with Article 38 verbatim. It must also meet the qualified/material lawrequirement sought by Article 13 and the specificity and predictability requirements mandated by Article 2. The vagueness of a norm has become a sufficient reason in itself for its unconstitutionality.

B. Statutory Basis: Article 2 of the Turkish Penal Code (TCK) No. 5237

These fundamental guarantees in the Constitution are embodied in Article 2 of the Turkish Penal Code (TCK) No. 5237, with a level of detail and clarity that even surpasses the Constitution.

TCK Article 2/1: “No one shall be penalized, and no security measure shall be applied, for an act that the law does not explicitly define as a crime. No penalty or security measure other than those written in the law shall be imposed.”. The word “explicitly” (açıkça) here is a strong legal emphasis on the principle of “specificity” (Lex Certa).
TCK Article 2/2: “Crimes and penalties cannot be established by the regulatory acts of the administration.”. This clause is a concrete guarantee of the separation of powers in criminal law, protecting the legislative body’s (TBMM) monopoly on creating crimes against the executive body (administration).
TCK Article 2/3: “Analogy cannot be used in the application of provisions of laws that contain crimes and penalties. Provisions containing crimes and penalties cannot be interpreted broadly in a way that leads to analogy.”. This clause clearly and jointly regulates the “prohibition of analogy” (Lex Stricta) and the “broad interpretation” problem, which is where this prohibition is most often violated.

Article 2 of the TCK transforms the abstract guarantee of Article 38 of the Constitution into a concrete armor against the two biggest threats encountered in practice: administrative and judicial activism. The legislator, by foreseeing these two dangerous paths, has explicitly banned them with TCK 2/2 and 2/3.

C. The Rationale (Ratio Legis) of TCK Article 2

The rationale of Article 2 of the TCK clearly reveals what the legislator intended with this article. According to the rationale, “in order to guarantee individual rights and freedoms,” “it is necessary that which acts constitute a crime be clearly determined in the law.” The rationale unequivocally emphasizes that this principle “is a requirement of the universal principle of ‘no crime and punishment without law'” and that the authority to define crimes and impose penalties belongs “only to the Turkish Grand National Assembly.”

3- What Sub-Guarantees Does the Principle of Legality Use to Protect the Individual Against the State’s Punitive Power?

The principle of legality is not an abstract philosophical ideal, but a practical mechanism that produces concrete and applicable guarantees in favor of the individual. These sub-guarantees bring the “guarantee function” of the principle to life.

A. Guarantee 1: “Specificity” and “Clarity” of Laws (Lex Certa)

The Lex Certa (specific law) principle expresses the quality dimension of the principle of legality. This principle imposes the obligation that the act constituting the crime and the corresponding sanction must be “shown in the law with clarity that leaves no room for doubt, is understandable, and has defined limits.”

Reflection in the TCK: The phrase “An act that the law does not explicitly define…” in TCK Art. 2/1 is the legal basis of this principle.
Purpose: The purpose of specificity is to ensure that individuals know prohibited acts in advance(predictability) and can freely regulate their behavior accordingly (legal certainty).
Example of Violation (AYM Precedent): The main battleground for the principle of legality in modern criminal law is the field of Lex Certa (specificity). The laws exist, but their content is vague. One of the most concrete examples of this is the objections brought before the Constitutional Court regarding the phrase “…committing a crime on behalf of the organization, despite not being a member of the organization…” in TCK Art. 220/6. In the objection petitions, it is argued that this phrase is “open to interpretation,” “lacks any framework defining its limits,” and therefore violates the “specificity” and “rule of law” principles in Article 2 of the Constitution. As emphasized in the freedom of expression and assembly decisions of the AYM (and the ECHR), such vagueness in criminal laws creates a “chilling effect” on individuals, de facto preventing the exercise of Constitutional rights.

B. Guarantee 2: Prohibition of Retroactive Application of Unfavorable Law (Lex Praevia)

The Lex Praevia (prior law) principle expresses the time dimension of the principle of legality. It is the individual’s guarantee to act according to the legal rules valid at the moment they perform their action and not to face rules enacted against them afterward.

This prohibition is twofold:

An act that was not a crime according to the laws in force at the time it was committed cannot be punished retroactively by a subsequently enacted law.
The penalty prescribed for that crime at the time the act was committed cannot be increased by a subsequently enacted law, and this increased penalty cannot be applied to acts committed before the law entered into force.

This principle prevents the state from setting “legal traps” for individuals by applying rules retroactively and forms the basis of legal certainty.

C. Guarantee 3: Prohibition of Analogy (Lex Stricta)

The Lex Stricta (strict law) principle expresses the interpretation dimension of the principle of legality. This principle is the absolute prohibition on a judge punishing an act not regulated in the law on the grounds that it “resembles” a crime that is regulated in the law (through analogy).

Reflection in the TCK: TCK Art. 2/3 explicitly provides for this prohibition, stating, “Analogy cannot be used in the application of provisions of laws that contain crimes and penalties.”
Example: If there is no law specifically criminalizing the act, downloading a movie from the internet without permission cannot be punished with a theft sentence by likening it to the crime of stealing a CD from a store (theft).
Precedent Analysis (Court of Cassation): The sensitivity of the Court of Cassation on this issue shows the fine line between analogy and interpretation. For example, TCK Art. 149, which regulates the crime of aggravated robbery, lists “in a residence” as an aggravating factor. In one case, the act was committed not in the “residence” itself, but in its “garden” (curtilage/appurtenance). The Court of Cassation ruled that “residence” and “appurtenance” are legally different concepts and that punishing the crime committed in the garden as if it were “committed in a residence” when “appurtenance” is not written in the law would violate the prohibition of analogy in TCK Art. 2/3. This decision shows how strictly one must adhere to the letter of the law.

D. Guarantee 4: Crimes and Penalties Cannot Be Established by the Regulatory Acts of the Administration (TCK 2/2)

This guarantee regulates the organic dimension of the principle of legality, i.e., the question of who can create a crime. Pursuant to TCK Art. 2/2, the authority to determine crimes and penalties belongs exclusively to the legislative body (TBMM). The executive body (Presidency, Ministries, Boards) cannot originally (directly) create crimes or determine penalties through regulatory acts such as regulations, decrees, communiqués, or circulars.

However, this principle also creates the most debated area in modern law: “Open / White / Blank Penal Laws” (Framework Laws).

In a modern, technical, and complex society (environmental law, IT, medicine, financial markets, etc.), it is practically impossible for the legislative body to regulate every technical detail within the text of the law. Therefore, the lawmaker resorts to the “framework law” method:

The law draws the basic framework of the crime (e.g., “Intentionally harming the environment is a crime”).
The law determines the sanction (the penalty) for this crime.
However, it leaves the authority to determine the technical details of which acts constitute “harming the environment” (e.g., which chemical, above which milligram amount, being released into water) to the administration (e.g., a regulation to be issued by the Ministry of Environment), within defined limits.

This method, referred to in doctrine as “white penal laws,” constitutes “one of the most controversial areas in our country regarding the principle of legality in crime and punishment” as to whether it violates the prohibition in TCK Art. 2/2. The Constitutional Court’s stance on this issue is aimed at striking a balance between these two necessities (legality and administrative flexibility): The legislative body must necessarily determine the basic elements, framework, and sanction of the crime itself; the area left to the administration must only be technical details with defined limits. If the delegation of authority turns into a delegation of the power to create crime (giving the administration a “blank check”), this will mean a violation of TCK Art. 2/2 and the Constitution (separation of powers).

Summary Table: Guarantees of the Principle of Legality

Latin Concept	Principle	Meaning (Brief Definition)	National Legal Basis (Main)
Lex Praevia	Prohibition of Retroactivity	A person cannot be punished for an act that was not a crime under the law at the time it was committed, or with a heavier penalty.	Const. Art. 38/1; TCK Art. 2/1, TCK Art. 7
Lex Certa	Principle of Specificity / Clarity	Crime definitions and penalties must be specific enough for individuals to know what is prohibited without any ambiguity.	Const. Art. 2 (Rule of Law); TCK Art. 2/1 (Law “explicitly” defines)
Lex Stricta	Prohibition of Analogy / Strict Interpretation	An act not explicitly defined as a crime in the law cannot be punished by likening it (through analogy) to a similar crime. Broad interpretation cannot amount to analogy.	TCK Art. 2/3
(TCK 2/2)	Prohibition on Admin. Creating Crimes	The executive body (administration) cannot create (ihdas) crimes through its own regulatory acts (regulations, etc.) without a law.	TCK Art. 2/2

4- What Are the Critical Nuances in the Application of the Principle of Legality? (The Difference Between Analogy and Interpretation, and Law in Favor of the Accused)

The application of the principle of legality is not always black and white. Judicial interpretation and changes in laws over time, in particular, bring with them complex legal nuances.

A. Critical Nuance 1: Prohibition of Analogy (Lex Stricta) vs. Broad Interpretation (TCK 2/3)

One of the most fundamental legal problems is this: Law is a field that, by its nature, requires interpretation. The judge must ascertain what the letter, purpose, and spirit of the legal text mean (literal, systematic, teleological interpretation). However, TCK Art. 2/3 has absolutely prohibited analogy. So, where does legitimate “interpretation” end, and where does forbidden “analogy” begin?

Interpretation: The mental activity aimed at revealing the meaning, scope, and purpose of an existing legal provision while remaining within that provision.
Analogy: The application of a rule regarding a similar, regulated situation to an unregulated situation (a gap in the law) (by stepping outside the provision).
Gray Area (Broad Interpretation): The problem arises in the area called “broad interpretation” (extensivinterpretation). Broad interpretation is possible even in criminal law.

To resolve this “gray area” and prevent judicial arbitrariness, the TCK No. 5237 (new TCK) added a very important phrase to Art. 2/3 that was not in the TCK No. 765 (old TCK). The article did not just say “analogy cannot be used,” it added this sentence: “Provisions containing crimes and penalties cannot be interpreted broadly in a way that leads to analogy.”.

This addition has a special meaning. During the old TCK period, there were serious criticisms that the prohibition of analogy was de facto breached or circumvented under the name of “broad interpretation” in judicial practice (especially in Court of Cassation rulings). The legislator of the new TCK saw these “negatives” and gave a clear message to the judiciary: The activity of interpretation is limited by the widest possible meaning of the law’s text. The moment interpretation goes beyond the letter of the law to create a new norm, it is no longer “broad interpretation” but forbidden “analogy.” The Court of Cassation’s “residence/appurtenance” decision is an example of strict interpretation in line with the spirit of this new provision.

B. Critical Nuance 2: Exception to Application Over Time: Retroactivity of the More Favorable Law (TCK 7)

The basic rule of the principle of legality was Lex Praevia (non-retroactivity of unfavorable law). However, this rule reverses completely in situations that are in favor of the perpetrator. This is the humanist exception to the principle.

TCK Article 7/2: This exception is regulated in Article 7 of the TCK, titled “Application in terms of time.” According to Article 7/2: “If the provisions of the law in force at the time the crime was committed and the law that entered into force afterward are different, the law that is in favor of the perpetrator shall be applied and executed.”.
Application (Determining the Favorable Law): It is not always clear which law is more favorable. The judge must compare the old and new law as a whole. For example, if the old law prescribes a prison sentence and the new law prescribes a judicial fine, the new law is more favorable. If both prescribe prison sentences, the durations (lower and upper limits) must be compared.
The Most Important Guarantee: “…and shall be executed”
- This phrase in TCK Art. 7/2 is revolutionary. It mandates that the favorable law be applied not only during the trial phase (until the verdict is given), but also after the verdict becomes final, i.e., during the execution (infaz) phase.
- For example, suppose a person received a 5-year prison sentence for an act, and the sentence became final and execution began. If, 2 years later, a favorable law is enacted that either decriminalizes that act or reduces its penalty to 1 year, this new law is applied retroactively. If the act is decriminalized, the convict is immediately released from prison, and all “legal consequences” of the sentence are nullified.

This situation may seem to conflict with the basic purpose of the principle of legality, which is legal certainty(predictability). However, here, the justice and social benefit purpose of criminal law prevails over the legal certainty purpose. If the legislator has enacted a new (favorable) law by accepting that an act no longer harms society (decriminalization) or deserves a lesser penalty (penalty reduction), continuing to punish the individual based on an old rule that is now considered “unjust” or “useless” would be contrary to the modern aims of criminal law. TCK Art. 7 is a declaration of justice that prefers substantive justice and social benefit over formal legal certainty.

5- How is the Principle of Legality Manifested in International Law and High Court Rulings?

The principle of legality is not just a national norm; it is also guaranteed as a fundamental human right in international law and high court precedents.

A. The International Standard: ECHR Article 7 and ECHR Precedent

The strongest basis for the principle in international law is Article 7 of the European Convention on Human Rights (ECHR), to which Turkey is a party. This article, titled “No Punishment Without Law,” is “part of our domestic law” under Article 90 of the Constitution and even holds a superior position in the hierarchy of norms.

The ECHR’s “Law” Standard: The European Court of Human Rights (ECHR) subjects the word “law” (kanun) in ECHR Art. 7 to a more material test than national courts. According to the ECHR, for a penal norm to be considered “law,” it must be:
1. Accessible (the citizen can access that rule) and
2. Foreseeable (specific and clear enough to allow the citizen to foresee the consequences of their action).
This “foreseeability” (specificity) test shows that the ECHR has transformed the Lex Certa principle into an international standard and directly supports the “specificity” review conducted by the Turkish Constitutional Court via Constitution Art. 2 (rule of law).
ECHR and Favorable Law (Scoppola v. Italy Ruling):
- For many years, the ECHR argued that ECHR Art. 7 did not, as TCK Art. 7 does, require the “retroactivity of favorable law,” and that this was an area left to the discretion of national states.
- However, the Court changed this precedent in the Scoppola v. Italy (Grand Chamber, 2009) case. With this historic decision, the ECHR clearly stated that ECHR Art. 7 not only prohibits the retroactivity of unfavorable law but “it also includes the requirement” of the retroactivity of the penal law that is more favorable to the offender.
- The meaning of this decision for Turkish law is this: The principle of “retroactivity of favorable law” regulated in TCK Art. 7 is no longer just a simple statutory regulation (TCK), but a fundamental human right standard under ECHR Art. 7, which is binding via Constitution Art. 90. Failure to apply this principle now means not only a violation of the TCK (Court of Cassation review) but also a violation of ECHR Art. 7 and a Constitutional right (AYM Individual Application).

B. National Judicial Review: The Judicial Guarantee of Legality

The protection of the principle of legality is subject to a two-tiered “dual-check” mechanism in Turkey. This structure aims to protect the principle from both judicial errors and errors originating from the legislature.

Court of Cassation (Yargıtay) (Review of the Law’s Application):
- The Court of Cassation reviews whether the first-instance courts and regional courts of appeal have correctly applied the existing laws (like TCK Art. 2 and TCK Art. 7).
- The Court of Cassation reviews judicial error (arbitrary interpretation, analogy, failure to apply favorable law).
- For example, when the Court of Cassation detects that TCK Art. 2 and 7 were not observed (e.g., failure to apply favorable settlement provisions) or that the prohibition of analogy was violated, it decides to “OVERTURN” (annul/remand) the local court’s decision.
Constitutional Court (AYM) (Review of the Law Itself):
- The AYM, on the other hand, reviews whether the law itself complies with the Constitution (Art. 38, 2, 13).
- The AYM reviews legislative error (vague law, unconstitutional crime definition).
- This review happens in two ways:
  - Norm Control (Abstract/Concrete): If a court finds a legal provision (e.g., TCK 220/6) it is applying in a case to be “vague” and unconstitutional, it can stop the trial and apply to the AYM for the annulment of this provision via the “objection path” (concrete norm control).
  - Individual Application: If a person has been convicted based on a vague legal provision (or by not applying the favorable law) and all domestic legal remedies, including the Court of Cassation, have been exhausted, they can make an individual application to the AYM on the grounds of “violation of the principle of legality.”

This dual-check structure forms a holistic guarantee system aimed at protecting the principle of legality from both the arbitrary interpretation of the judiciary (Court of Cassation review) and the arbitrary or poor-quality drafting of the legislature (AYM review).

Drawing the Borders of the Rule of Law

The principle of legality in crime and punishment was born in the 18th-century Age of Enlightenment as a philosophical rebellion against the arbitrariness of absolute powers and judges, and today it has become an indispensable element of the rule of law. This principle is not a simple technical criminal rule, but a fundamental political and legal boundary stone that defines the limits of the state’s punitive power and the individual’s sphere of freedom.

This principle, placed under a multi-layered armor by TCK Art. 2, Constitution Art. 38, and ECHR Art. 7 in the international arena, has a dynamic structure. Today, the struggle for legality continues not over the “absence of law” as in the 18th century, but in more complex and modern areas such as “vague and ambiguous laws” (Lex Certa violation) and “framework laws that delegate excessive authority to the administration” (TCK 2/2 violation). The dual judicial review provided by the Court of Cassation and the Constitutional Court is of vital importance for protecting this fundamental principle as an unwavering guarantor of the rule of law.

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