Understanding the Basics of International Law: Treaties, Custom, and Sovereign Immunity

The Decentralized Nature of International Law

Unlike domestic legal systems that feature a centralized legislative parliament, police force, and mandatory courts, the international legal order is decentralized, governed by the principle of sovereign equality of states. International law relies primarily on state consent, mutual reciprocity, treaty commitments, and collective diplomatic and economic enforcement.

The Sources of International Law (Article 38, ICJ Statute)

Courts and arbitral tribunals adjudicating international legal disputes consult a recognized hierarchy of sources:

1. International Conventions and Treaties: Express written agreements between states creating binding legal obligations. Governed by the foundational customary principle pacta sunt servanda ("agreements must be kept"), codified in the 1969 Vienna Convention on the Law of Treaties.
2. Customary International Law: Unwritten legal obligations requiring two distinct elements:
   • State Practice (Diuturnitas): Consistent, widespread, and general practice by states over time.
   • Opinio Juris Sive Necessitatis: The subjective belief by states that the practice is rendered obligatory by a legal duty, rather than mere diplomatic courtesy or habit.
3. General Principles of Law: Universal legal maxims recognized across domestic legal systems worldwide (e.g. good faith, estoppel, res judicata).
4. Judicial Decisions and Scholarly Teachings: Subsidiary means for the determination of rules of law, including decisions of international tribunals (ICJ, ITLOS) and leading academic publications.

Jus Cogens: Peremptory Norms

Certain fundamental principles of international law are classified as jus cogens (peremptory norms). These norms are so fundamental that no derogation is permitted by any state under any circumstances, and any treaty in conflict with a jus cogens norm is void ab initio. Recognized jus cogens norms include prohibitions against genocide, maritime piracy, slavery, torture, and wars of aggression.

Sovereign Immunity and the FSIA

Under international law, sovereign states enjoy immunity from being sued in the domestic courts of other nations. In the United States, this doctrine is codified in the Foreign Sovereign Immunities Act (FSIA) of 1976 (28 U.S.C. § 1602). Foreign governments are immune from U.S. lawsuits unless a specific statutory exception applies, most notably the Commercial Activity Exception (where the foreign state engages in commercial conduct having direct effects in the United States).

Key Legal Next Steps

1. Determine whether a dispute with a foreign entity falls under the Commercial Activity exception of the Foreign Sovereign Immunities Act.
2. Identify whether customary international law or ratified treaty covenants supply enforceable rules of decision in domestic litigation.
3. Incorporate clear choice-of-law and international arbitration forum selection clauses into cross-border contracts.