Introduction
The relationship between the Turkish Constitution and international treaties is one of the most important subjects in Turkish constitutional law. It determines how international obligations enter domestic law, how courts should apply international agreements, how human rights treaties interact with ordinary laws, and how individuals may rely on international human rights standards before Turkish courts.
The key constitutional provision is Article 90 of the Constitution of the Republic of Türkiye. Article 90 regulates the ratification of international treaties and their domestic legal effect. It provides that international agreements duly put into effect have the force of law. More importantly, it states that in case of conflict between domestic laws and international agreements concerning fundamental rights and freedoms, the provisions of international agreements shall prevail.
This rule gives international human rights treaties a special position in Turkish law. It does not make every international treaty superior to the Constitution, but it does require domestic authorities to give priority to human rights treaties over conflicting ordinary statutes. Therefore, Article 90 is a bridge between Turkish constitutional law, international law and human rights protection.
1. Constitutional Basis: Article 90 of the Turkish Constitution
Article 90 is titled “Ratification of international treaties.” It provides that the ratification of treaties concluded with foreign states and international organizations on behalf of Türkiye is subject to approval by the Grand National Assembly of Türkiye through a law approving ratification. This means that many treaties require parliamentary participation before they become binding in domestic law.
The same article also states that international agreements duly put into effect have the force of law. This phrase is critical. Once an international treaty is properly ratified and put into effect, it becomes part of the Turkish legal order and may be relied upon as a legal norm.
However, Article 90 also contains a special rule for international agreements concerning fundamental rights and freedoms. If there is a conflict between domestic laws and such international agreements, the treaty provisions prevail. This gives human rights treaties a privileged status over ordinary statutes in conflict situations.
2. The Domestic Legal Effect of International Treaties
Under Turkish constitutional law, international treaties duly put into effect have the force of law. This means that they are not merely political commitments or diplomatic declarations. They are legally relevant within the domestic system. Courts, administrative authorities and legal practitioners may need to consider treaty provisions when deciding disputes.
This domestic legal effect is especially important in areas such as human rights, investment law, trade law, tax law, criminal cooperation, migration, family law, intellectual property, arbitration and diplomatic relations. A treaty may create obligations for the State, rights for individuals, procedural duties for courts or interpretive standards for administrative authorities.
However, the exact domestic effect of a treaty may depend on its wording, nature and implementation mechanism. Some treaty provisions are sufficiently clear and directly applicable. Others may require implementing legislation. Therefore, lawyers must examine the treaty text carefully and determine whether the provision can be invoked directly before domestic authorities.
3. Article 90 and the Hierarchy of Norms
The hierarchy of norms determines which legal rule prevails when two rules conflict. In Türkiye, the Constitution is the supreme legal norm. Article 11 provides that constitutional provisions are binding fundamental legal rules and that laws cannot be contrary to the Constitution.
International treaties duly put into effect have the force of law under Article 90. Therefore, as a general rule, they are treated as legal norms within the domestic legal system. But international treaties concerning fundamental rights and freedoms have an additional advantage: they prevail over ordinary domestic laws in case of conflict.
This creates a special hierarchy. The Constitution remains the supreme norm. Ordinary statutes and international treaties generally have the force of law. But in the specific field of fundamental rights and freedoms, a human rights treaty prevails over a conflicting ordinary statute.
This structure is crucial in litigation. If a domestic law restricts a fundamental right more severely than an international human rights treaty allows, a court should prefer the treaty standard.
4. The 2004 Amendment and Human Rights Treaties
The privileged status of international human rights treaties was introduced by constitutional amendment in 2004. The Constitutional Court’s 2025 Annual Report notes that the Turkish Constitution was amended in 2004 to recognize the supremacy of international conventions on fundamental rights and freedoms to which Türkiye is a party.
This amendment was a major turning point. Before the amendment, international treaties had the force of law, but the relationship between treaties and later or conflicting domestic laws was more controversial. The 2004 amendment clarified that human rights treaties prevail in case of conflict with ordinary statutes.
The purpose of this rule is to strengthen rights protection and ensure that Türkiye’s international human rights obligations are applied domestically. It also encourages courts to interpret domestic law consistently with international human rights standards.
5. International Human Rights Treaties and Domestic Courts
Article 90 directly affects the duties of Turkish courts. When a case involves fundamental rights and freedoms, courts should not limit their analysis to domestic statutes. They should also consider relevant international human rights treaties. This is particularly important where domestic law is ambiguous, restrictive or potentially inconsistent with international standards.
For example, in cases involving freedom of expression, fair trial, property rights, privacy, religious freedom, equality, personal liberty, family life or prohibition of ill-treatment, courts may need to consider the European Convention on Human Rights and other relevant human rights treaties.
This does not mean that every case automatically turns into an international law dispute. But where the dispute concerns fundamental rights and a treaty provision is relevant, Article 90 requires serious consideration of the international standard.
6. The European Convention on Human Rights and Turkish Constitutional Law
The European Convention on Human Rights has a particularly important place in Turkish constitutional law. This is because individual application before the Constitutional Court is connected to rights protected by both the Constitution and the European Convention on Human Rights. Article 148 of the Constitution provides that everyone may apply to the Constitutional Court alleging that a fundamental right or freedom within the scope of the European Convention on Human Rights and guaranteed by the Constitution has been violated by public authorities, after ordinary remedies are exhausted.
This creates what is often described as a “joint protection area” between the Constitution and the Convention. A right must generally be protected by the Constitution and fall within the scope of the Convention system for individual application purposes.
As a result, the Convention is not merely an external source. It directly shapes constitutional adjudication in Türkiye. The Constitutional Court interprets many rights, such as fair trial, property, expression, privacy, liberty and effective remedy, in light of both constitutional provisions and Convention standards.
7. Article 90 and Article 148: Two Connected Mechanisms
Article 90 and Article 148 perform different but connected functions. Article 90 determines the domestic legal effect of international treaties and gives priority to human rights treaties over conflicting ordinary laws. Article 148 regulates individual application before the Constitutional Court and links this remedy to rights within the scope of the European Convention on Human Rights.
Together, these provisions create a strong human rights protection framework. Article 90 allows courts to apply international human rights treaties directly or prefer them over conflicting laws. Article 148 allows individuals to bring constitutional complaints when public authorities violate rights within the joint constitutional and Convention protection area.
For lawyers, this means that human rights treaty arguments should be raised early before ordinary courts. If the case later reaches the Constitutional Court, the applicant can show that treaty-based and constitutional arguments were properly presented.
8. International Treaties and Constitutional Interpretation
International treaties also influence constitutional interpretation. Courts may use treaty provisions to interpret domestic constitutional rights more effectively. For example, constitutional guarantees of fair trial, property, freedom of expression and privacy may be interpreted in harmony with the European Convention on Human Rights and the case-law of the European Court of Human Rights.
The Constitutional Court’s official materials emphasize that all judicial authorities are obliged to resolve disputes in accordance with fundamental rights guaranteed under the Constitution, which has contributed to the constitutionalisation of different fields of law.
This interpretive function is important even where there is no direct conflict between a domestic law and a treaty. If domestic law can be interpreted in two ways, courts should generally prefer the interpretation that is more compatible with constitutional rights and international human rights obligations.
9. Treaties Concerning Fundamental Rights and Freedoms
Not every international treaty receives the special priority rule under Article 90. The privileged conflict rule applies specifically to international agreements concerning fundamental rights and freedoms. This category includes human rights treaties, such as the European Convention on Human Rights and other international instruments protecting civil, political, social, economic or cultural rights.
The practical question is whether the treaty provision invoked concerns a fundamental right or freedom. If it does, and if it conflicts with an ordinary domestic law, Article 90 requires the treaty provision to prevail.
This distinction matters. A trade treaty, tax treaty or technical cooperation treaty may have the force of law, but it may not automatically enjoy the same priority rule unless the provision at issue concerns fundamental rights and freedoms. Lawyers must therefore identify the nature of the treaty and the specific provision relied upon.
10. International Treaties and Ordinary Laws
When an international treaty does not concern fundamental rights and freedoms, it still has the force of law once duly put into effect. However, Article 90’s special priority clause applies only to treaties concerning fundamental rights and freedoms.
This means that the relationship between non-human-rights treaties and ordinary laws may require more detailed legal analysis. Courts may need to consider the treaty’s nature, the date of enactment, special law-general law principles, implementing legislation and the subject matter of the dispute.
In practice, many treaty-related disputes involve international tax agreements, investment treaties, arbitration conventions, commercial treaties, double taxation agreements, extradition treaties or mutual legal assistance treaties. These agreements may be highly important, but their domestic application depends on the constitutional and statutory framework.
11. International Treaties and Fundamental Rights Litigation
In fundamental rights litigation, Article 90 is a powerful tool. It can support claims in constitutional, administrative, civil, criminal, labor and family law cases. For example, a person alleging violation of fair trial rights may rely on both Article 36 of the Constitution and Article 6 of the European Convention on Human Rights. A property dispute involving public interference may invoke Article 35 of the Constitution and Article 1 of Protocol No. 1 to the Convention.
The practical advantage of Article 90 is that it prevents domestic law from being applied in a way that contradicts binding human rights treaty obligations. If a domestic statute is narrower than a human rights treaty, the treaty standard may prevail in the specific conflict.
However, treaty arguments should be precise. A petition should identify the treaty provision, explain why it concerns fundamental rights, show the conflict with domestic law and state why Article 90 requires priority.
12. International Treaties and the Right to a Fair Trial
The right to a fair trial is one of the most common fields where international treaties influence Turkish law. Article 36 of the Turkish Constitution protects the right to litigation and fair trial, while Article 6 of the European Convention on Human Rights provides detailed fair trial guarantees.
Through Article 90 and Article 148, fair trial standards such as access to court, independent and impartial tribunal, equality of arms, adversarial proceedings, reasoned judgment, reasonable time and enforcement of final judgments have become central in Turkish constitutional practice.
In litigation, fair trial treaty standards may be relevant where domestic procedural rules are applied excessively formalistically, where parties are denied effective participation, where judgments lack sufficient reasoning or where final court decisions are not enforced.
13. International Treaties and Freedom of Expression
Freedom of expression is another field where international treaties are highly influential. Article 26 of the Constitution protects freedom of expression, while Article 10 of the European Convention on Human Rights protects the right to express and receive information and ideas.
When domestic restrictions on expression are assessed, courts should consider legality, legitimate aim, necessity in a democratic society and proportionality. These standards are central to both Turkish constitutional law and the Convention system.
Article 90 may be particularly important if a domestic law or its interpretation imposes a restriction broader than international human rights standards allow. In such cases, courts should prefer the rights-protective treaty standard.
14. International Treaties and Property Rights
Property rights are protected under Article 35 of the Turkish Constitution. They are also protected under Article 1 of Protocol No. 1 to the European Convention on Human Rights. In cases involving expropriation, zoning restrictions, tax burdens, administrative fines, seizure, non-enforcement of judgments or investment-related measures, international treaty standards may be relevant.
The key concepts are legality, public interest and fair balance. Public authorities may interfere with property rights, but they must not impose an excessive individual burden. Article 90 strengthens the argument that domestic property restrictions should be interpreted consistently with international standards.
For companies and investors, this interaction is especially important. Public measures affecting assets may raise both constitutional property claims and treaty-based arguments.
15. International Treaties and Foreigners
International treaties are particularly important for foreigners. Article 16 of the Constitution provides that the fundamental rights and freedoms of aliens may be restricted by law compatible with international law. This means that international law is expressly built into the constitutional framework governing foreigners.
Foreigners may rely on international human rights standards in cases involving deportation, administrative detention, residence, family life, protection against ill-treatment, property rights, access to court and effective remedy.
For example, a deportation decision may raise issues under the prohibition of torture or inhuman treatment if the person faces a real risk in the destination country. In such cases, domestic authorities must consider both constitutional guarantees and international obligations.
16. International Investment Treaties and Constitutional Law
International treaties are also important in investment law. Türkiye is party to various bilateral investment treaties and international arbitration instruments. These treaties may protect foreign investors through standards such as fair and equitable treatment, protection against unlawful expropriation, non-discrimination and access to arbitration.
Although investment treaties are not always “fundamental rights treaties” under Article 90’s special priority clause, they may still have domestic and international legal significance once duly put into effect. They may also interact with constitutional property rights, administrative law and access to remedies.
Foreign investors may therefore need to consider both constitutional remedies before Turkish courts and treaty-based remedies such as arbitration, depending on the applicable legal framework and dispute resolution clauses.
17. International Treaties and Criminal Law
International treaties may affect criminal law in areas such as extradition, mutual legal assistance, transfer of sentenced persons, cybercrime, corruption, organized crime, terrorism financing and human rights protections in criminal proceedings.
However, criminal law is strongly governed by legality. Article 38 of the Constitution protects legality of offences and penalties, non-retroactivity and presumption of innocence. International treaties may support cooperation and procedural standards, but criminal punishment must still rest on domestic legal basis and constitutional safeguards.
In criminal proceedings, human rights treaties may strengthen arguments concerning fair trial, liberty, defense rights, prohibition of torture, unlawfully obtained evidence and effective remedy.
18. International Treaties and Administrative Law
Administrative authorities are also bound by treaty obligations where applicable. This is especially important in immigration, public procurement, taxation, customs, environmental regulation, investment permits, public employment and social security matters.
Article 125 provides that judicial review is available against administrative acts and actions. If an administrative act violates an international human rights treaty, especially where fundamental rights are involved, the affected person may raise Article 90 before administrative courts.
For example, an administrative detention measure involving a foreigner may require consideration of international human rights standards on liberty and effective remedy. A public authority’s interference with property may require fair balance analysis. A restriction on association or expression may require democratic necessity review.
19. Practical Litigation Strategy Based on Article 90
A strong Article 90 argument should be structured carefully. First, identify the relevant international treaty and confirm that it has been duly put into effect. Second, identify the specific treaty provision. Third, explain whether the provision concerns fundamental rights and freedoms. Fourth, identify the domestic law or administrative practice that conflicts with the treaty. Fifth, explain why the treaty standard must prevail.
The argument should not be abstract. It should connect the treaty provision to the facts of the case. For example, in a fair trial case, the petition should explain how the domestic procedure violated Article 6 of the European Convention on Human Rights. In a property case, it should explain why the public measure failed to maintain a fair balance. In a deportation case, it should explain the concrete risk of ill-treatment.
Constitutional and treaty arguments should be raised before ordinary courts. This is important because individual application before the Constitutional Court is subsidiary and generally requires exhaustion of ordinary remedies.
20. Conclusion
The relationship between the Turkish Constitution and international treaties is governed primarily by Article 90. This provision gives international agreements duly put into effect the force of law and provides a special priority rule for international agreements concerning fundamental rights and freedoms. Where such treaties conflict with ordinary domestic laws, treaty provisions prevail.
This relationship is especially important in human rights law. The 2004 constitutional amendment strengthened the domestic position of international human rights treaties by recognizing their priority over conflicting laws in the field of fundamental rights and freedoms.
The European Convention on Human Rights has a particularly strong role because individual application before the Constitutional Court is linked to rights protected by both the Constitution and the Convention system. Article 148 allows individuals to apply to the Constitutional Court after ordinary remedies are exhausted when a public authority violates a constitutional right within the scope of the European Convention on Human Rights.
For lawyers, individuals, companies and foreign investors, Article 90 is a practical legal tool. It may affect fair trial claims, freedom of expression disputes, property cases, deportation matters, administrative litigation, criminal proceedings, labor law, social rights and investment-related disputes.
Ultimately, international treaties do not stand outside the Turkish legal system. Once duly put into effect, they become part of domestic law. In the field of fundamental rights and freedoms, they may even prevail over conflicting ordinary statutes. This makes Article 90 one of the most important bridges between Turkish constitutional law and international legal protection.
FAQ: The Relationship Between the Turkish Constitution and International Treaties
What is the main constitutional provision on international treaties in Türkiye?
The main provision is Article 90 of the Constitution of the Republic of Türkiye.
Do international treaties have domestic legal effect in Türkiye?
Yes. International agreements duly put into effect have the force of law under Article 90.
Do international treaties prevail over Turkish laws?
International agreements concerning fundamental rights and freedoms prevail over conflicting domestic laws. Other treaties have the force of law, but the special priority rule applies specifically to fundamental rights treaties.
Is the Constitution below international treaties?
No. The Constitution remains the supreme domestic legal norm. Article 90 gives priority to human rights treaties over ordinary laws, not over the Constitution itself.
Why is the 2004 amendment important?
The 2004 amendment introduced the rule that international agreements concerning fundamental rights and freedoms prevail over conflicting domestic laws.
Why is the European Convention on Human Rights important in Türkiye?
It is central because individual application before the Constitutional Court is linked to rights protected by both the Turkish Constitution and the European Convention on Human Rights.
Can Turkish courts apply international human rights treaties directly?
Yes, where the treaty is duly put into effect and the relevant provision is applicable. In case of conflict with domestic law concerning fundamental rights, the treaty provision prevails.
Can Article 90 be used in ordinary litigation?
Yes. Lawyers may rely on Article 90 in civil, criminal, administrative, labor, family, property and constitutional cases where international treaty standards are relevant.
Can foreigners rely on international treaties in Türkiye?
Yes. Foreigners may rely on relevant international human rights treaties, especially in deportation, detention, family life, property and fair trial cases.
Why is Article 90 important for human rights protection?
Because it ensures that Türkiye’s international human rights obligations are not merely external commitments, but legal standards that may prevail over conflicting domestic laws.
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