The relationship between international law and domestic (municipal) law is a fundamental aspect of a state's legal system. India, like many other countries, generally adopts a dualist approach, meaning international law does not automatically become part of its domestic legal order. It requires specific acts of transformation or incorporation.

How International Law Becomes Part of Indian Law:

1. Constitutional Provisions:

   • Article 51(c): This Directive Principle of State Policy mandates that the State shall endeavor to "foster respect for international law and treaty obligations in the dealings of organized peoples with one another." While not directly enforceable, it serves as a guiding principle for the executive and judiciary to interpret domestic law in harmony with international obligations.
   • Article 253: This article grants Parliament the exclusive power to make any law "for implementing any treaty, agreement or convention with any other country or countries or any decision made at any international conference, association or other body." This is the primary constitutional mechanism for transforming international treaties into domestic law. Once Parliament enacts a law under Article 253, the treaty provisions become part of the 'law of the land'.

2. Judicial Incorporation and Interpretation:

   • Customary International Law (CIL): Indian courts have generally held that customary international law, which is not inconsistent with existing domestic statutes or the Constitution, is considered part of Indian law without the need for specific legislative enactment. Courts often use CIL to interpret ambiguous domestic laws or to fill gaps in the domestic legal framework.
   • Treaties (without specific legislation): While treaties generally require parliamentary legislation under Article 253 to be directly enforceable, the Indian judiciary, particularly the Supreme Court, has adopted a progressive stance. In the absence of conflicting domestic law, and especially in the realm of human rights, courts have increasingly referred to and applied international conventions and norms, even without specific enabling legislation. This is often done by interpreting domestic statutes in a manner consistent with India's international obligations.
   • Landmark Cases:
     • Vishaka v. State of Rajasthan (1997): The Supreme Court, in the absence of specific domestic legislation, laid down guidelines to prevent sexual harassment at the workplace, explicitly drawing upon the Convention on the Elimination of All Forms of Discrimination Against Women (CEDAW) and other international instruments. The Court held that international conventions and norms are to be read into domestic laws in the absence of inconsistent domestic law.
     • D.K. Basu v. State of West Bengal (1997): The Court issued guidelines on custodial torture, referring to the International Covenant on Civil and Political Rights (ICCPR) and the Convention Against Torture (CAT), emphasizing that human rights are universal and cannot be curtailed by domestic law.
     • Kesavananda Bharati v. State of Kerala (1973): While not directly on international law, this case established the 'basic structure doctrine', and subsequent judgments have indicated that international law can be used to interpret fundamental rights, provided it does not contradict the basic structure.

Conflict Between International Law and Municipal Law:

In the event of a direct and irreconcilable conflict between a domestic statute enacted by the Indian Parliament and a rule of international law (whether treaty or customary), the municipal courts of India will generally apply the domestic law. This principle stems from the dualist nature of the Indian legal system and the doctrine of parliamentary sovereignty.

• Supremacy of Domestic Legislation: If Parliament has enacted a law that clearly contradicts an international obligation, that domestic law will prevail within the Indian legal system. The rationale is that the judiciary's role is to interpret and apply the laws made by the sovereign legislature.
• Presumption of Conformity: However, courts will always attempt to interpret domestic law in a manner that is consistent with India's international obligations, if such an interpretation is reasonably possible. This is known as the 'presumption of conformity' or 'harmonious construction'. Only when such an interpretation is impossible will the domestic law prevail.
• International Responsibility: While domestic law prevails in municipal courts, India would incur international responsibility for breaching its international obligations. The remedy for such a breach would lie at the international plane (e.g., through diplomatic protests, international dispute settlement mechanisms), not in domestic courts invalidating the statute.

In summary, international law enters the Indian legal system primarily through parliamentary legislation, but also significantly through judicial interpretation and incorporation, especially in the human rights domain. However, in a direct conflict, the principle of parliamentary sovereignty dictates that domestic law will be applied by Indian municipal courts, though courts strive to avoid such conflicts through harmonious interpretation.