Key Concepts of International Law

Why This Matters

International law isn't just a set of abstract rules—it's the framework that explains why states cooperate, when they can legally use force, and how the international system maintains order without a world government. You're being tested on your ability to understand the tension between state sovereignty and collective norms, the mechanisms that enforce compliance, and the exceptions that prove the rules. These concepts appear constantly in questions about intervention, treaty compliance, human rights, and the legitimacy of international institutions.

Don't just memorize definitions—know what problem each principle solves and where principles conflict with each other. Can a state invoke sovereignty to block humanitarian intervention? When does self-determination clash with territorial integrity? These tensions are where exam questions live. Master the relationships between concepts, and you'll be ready for anything from multiple choice to complex FRQ scenarios.

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Foundational Principles of the State System

These principles establish the basic architecture of international relations: who the key actors are, what rights they possess, and why the system treats states as the primary units. Without these foundations, international law would have no subjects to govern.

State Sovereignty

• Ultimate authority over territory and domestic affairs—this is the bedrock principle that makes states the primary actors in international relations
• Independence from external control means no higher authority can legally dictate a state's internal policies without consent
• Foundational to the Westphalian system—understanding sovereignty explains why international law relies on consent rather than enforcement

Equality of States

• Legal equality regardless of size or power—Liechtenstein has the same formal rights as China in international law
• One state, one vote in most international organizations reflects this principle, though de facto power imbalances persist
• Non-discrimination in international dealings underpins the legitimacy of institutions like the UN General Assembly

Territorial Integrity

• Right to maintain boundaries against external aggression or forced annexation
• Closely linked to sovereignty—you can't have meaningful self-governance if your borders aren't secure
• Violations trigger international responses, from condemnation to sanctions to collective security actions

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Principles Governing State Behavior

These rules constrain how states interact, establishing boundaries between legitimate and illegitimate conduct. They transform raw power politics into a rule-governed system.

Non-Intervention

• Prohibition on interfering in internal affairs—extends to political, economic, and military meddling
• Upholds sovereignty by creating a legal barrier against great power manipulation of weaker states
• Contested exceptions exist for humanitarian crises, UN-authorized actions, and invited interventions

Prohibition of Use of Force

• Armed force against another state is generally illegal under Article 2(4) of the UN Charter
• Two recognized exceptions: self-defense (Article 51) and UN Security Council authorization
• Central to post-WWII order—this principle distinguishes modern international law from earlier "might makes right" systems

Peaceful Settlement of Disputes

• Negotiation, mediation, arbitration, and adjudication are the preferred mechanisms
• Prevents escalation by providing legitimate alternatives to military action
• International Court of Justice and regional bodies institutionalize this principle

Reciprocity

• Mutual treatment expectations encourage compliance—states follow rules partly because they want others to do the same
• Enforcement mechanism without enforcement—reciprocity creates incentives for cooperation in an anarchic system
• Shapes diplomatic relations and trade, where tit-for-tat dynamics can either build trust or escalate conflicts

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Human Rights and Humanitarian Principles

These concepts represent the tension between state sovereignty and universal values. They assert that some rights transcend borders and limit what states can do even within their own territory.

Respect for Human Rights

• States must protect individuals within their jurisdiction—this obligation exists regardless of citizenship
• Enshrined in treaties like the ICCPR, ICESCR, and regional conventions (European, Inter-American, African)
• Creates accountability through monitoring bodies, courts, and the possibility of international condemnation

Self-Determination of Peoples

• Right to determine political status and pursue economic, social, and cultural development
• Drove decolonization and continues to fuel debates about secession, autonomy, and indigenous rights
• Tension with territorial integrity—when does a "people" have the right to break away from an existing state?

Non-Refoulement

• Cannot return refugees to danger—states must not send asylum seekers back to face persecution, torture, or death
• Cornerstone of refugee law under the 1951 Refugee Convention
• Absolute prohibition that applies even to individuals who entered illegally or committed crimes

Jus Cogens (Peremptory Norms)

• Non-derogable principles that no treaty or state action can override—the constitutional law of the international system
• Includes prohibitions on genocide, torture, slavery, and crimes against humanity
• Universally binding regardless of whether a state has consented to specific treaties

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Treaty Law and Compliance Mechanisms

These principles explain why international agreements work and what happens when they don't. They address the fundamental puzzle of how commitments can be credible without a world police force.

Pacta Sunt Servanda

• "Agreements must be kept"—the foundational principle that makes treaty law meaningful
• Codified in the Vienna Convention on the Law of Treaties (Article 26)
• Enables long-term cooperation by establishing that commitments survive changes in government or circumstances

Good Faith

• Honest and fair dealing in negotiations, treaty interpretation, and implementation
• Prevents technical compliance with bad intent—states can't exploit loopholes while violating the spirit of agreements
• Underpins trust in a system where enforcement depends heavily on reputation

International Responsibility

• States are accountable for breaches of international obligations
• Consequences include reparations, restitution, and satisfaction (formal acknowledgment of wrongdoing)
• Reinforces rule of law by establishing that violations have costs, even without centralized enforcement

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Diplomatic and Institutional Frameworks

These principles enable the day-to-day functioning of international relations by protecting the channels through which states communicate and cooperate.

Diplomatic Immunity

• Diplomats cannot be prosecuted or sued in the host country—covers criminal and most civil matters
• Governed by the Vienna Convention on Diplomatic Relations (1961)
• Ensures safe conduct so states can maintain communication even during conflicts or tensions

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Quick Reference Table

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Self-Check Questions

1. Which two principles most directly conflict when a minority group seeks independence from an existing state? Explain how international law attempts to balance them.

2. Identify three principles that limit state sovereignty. For each, explain what type of state action it prohibits or requires.

3. Compare pacta sunt servanda and good faith: How do these principles work together to ensure treaty compliance? What gap would exist if only one applied?

4. If an FRQ asks you to evaluate the legality of a military intervention, which principles would you analyze? Under what conditions might the intervention be legal?

5. How does jus cogens differ from ordinary international law? Give two examples of jus cogens norms and explain why they cannot be overridden by treaty.