International Law: Treaties & Custom

Active learning helps students grasp the abstract nature of international law by making its sources tangible. Debates, simulations, and case studies transform treaty negotiations and customary practices from distant concepts into concrete, interactive experiences that build retention and critical thinking.

• Year 10
• Citizenship
• 4 activities
• 30 min–50 min

Learning Objectives

1. Compare the legal standing of a ratified treaty with a long-standing customary international practice.
2. Analyze the mechanisms by which international law is created through state consent and general practice.
3. Evaluate the effectiveness of international legal enforcement in situations where state sovereignty is asserted.
4. Explain the role of international organizations, such as the International Court of Justice, in adjudicating disputes under international law.

Document Mystery

⏱ 40 min·Pairs

Debate Pairs: Treaty vs Customary Law

Pair students to prepare arguments: one side defends treaties as clearer and more reliable, the other praises customary law's flexibility. Each pair presents for 3 minutes, then switches sides. Class votes on strongest points and discusses real examples like the Geneva Conventions.

Prepare & details

Explain the difference between international treaties and customary international law.

Facilitation Tip: During the Debate Pairs activity, circulate to ensure each pair has clear roles and pre-selected cases to compare, preventing vague or unfocused discussions.

Setup: Groups at tables with document sets

Materials: Document packet (5-8 sources), Analysis worksheet, Theory-building template

• Analyze
• Evaluate
• Self-Management
• Decision-Making

Simulation Game

⏱ 50 min·Small Groups

Simulation Game: Mock UN Treaty Negotiation

Assign roles as state representatives with conflicting interests, such as environmental vs economic priorities. Groups draft a short treaty over 20 minutes, then present for ratification vote. Debrief on ratification challenges and sovereignty issues.

Prepare & details

Analyze how international law is created and enforced.

Facilitation Tip: For the Mock UN Treaty Negotiation, provide a structured negotiation guide with clear time limits and topic parameters to keep the simulation focused and productive.

Setup: Flexible space for group stations

Materials: Role cards with goals/resources, Game currency or tokens, Round tracker

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Document Mystery

⏱ 45 min·Small Groups

Case Study Carousel: Enforcement Examples

Set up stations with cases like the ICJ Nicaragua ruling or UN sanctions on North Korea. Small groups rotate, noting creation, enforcement attempts, and sovereignty hurdles. Each group shares one insight in a whole-class summary.

Prepare & details

Assess the challenges of state sovereignty in the application of international law.

Facilitation Tip: In the Case Study Carousel, assign small groups to specific stations and rotate roles so everyone engages with each enforcement example, avoiding passive observation.

Setup: Groups at tables with document sets

Materials: Document packet (5-8 sources), Analysis worksheet, Theory-building template

• Analyze
• Evaluate
• Self-Management
• Decision-Making

Document Mystery

⏱ 30 min·Individual

Timeline Individual: Evolution of a Custom

Students research one custom, such as maritime boundaries, and create a timeline of practices leading to legal status. Include key treaties that codified it. Share digitally or on posters for class gallery walk.

Prepare & details

Explain the difference between international treaties and customary international law.

Facilitation Tip: For the Timeline Individual activity, supply a mix of primary and secondary sources to help students trace the evolution of customs accurately and efficiently.

Setup: Groups at tables with document sets

Materials: Document packet (5-8 sources), Analysis worksheet, Theory-building template

• Analyze
• Evaluate
• Self-Management
• Decision-Making

Teaching This Topic

Teach this topic by balancing theory with lived experience. Start with a brief overview, then immerse students in activities that require them to apply concepts. Research shows that simulations and case studies build empathy and understanding of sovereignty’s role, while debates sharpen analytical skills. Avoid overloading with legal jargon; focus on the purpose and impact of each source instead.

What to Expect

Successful learning looks like students distinguishing between treaties and customs in real time, articulating why enforcement varies, and connecting historical examples to current global issues. They should confidently explain how these sources shape state behavior and international cooperation.

Watch Out for These Misconceptions

Common Misconception

During Debate Pairs, watch for students assuming all international law comes from treaties.

What to Teach Instead

Use the debate format to have pairs compare a treaty-based agreement, like the Paris Climate Agreement, with a customary practice, such as the prohibition of slavery. Ask them to identify how each source binds states differently and why customary law persists even without formal ratification.

Common Misconception

During Mock UN Treaty Negotiation, watch for students expecting international law to work like domestic law with centralized enforcement.

What to Teach Instead

During the simulation, emphasize state consent and voluntary compliance by including a clause in the negotiation guide that allows states to opt out of enforcement mechanisms. Debrief by asking groups to reflect on why enforcement is often weak or inconsistent in real negotiations.

Common Misconception

During Case Study Carousel, watch for students believing treaties automatically bind all countries.

What to Teach Instead

Use the carousel stations to present examples of treaties with varying ratification rates, such as the Convention on the Rights of the Child. Ask students to note which countries have not ratified each treaty and discuss how customary law might still apply to those cases.

Assessment Ideas

Discussion Prompt

After Debate Pairs, pose the following to small groups: 'Imagine a new global crisis emerges requiring immediate international cooperation. Would it be more effective to create a new treaty or rely on existing customary international law? Justify your answer with specific examples of challenges and benefits for each.' Allow groups 10 minutes to discuss before sharing key points.

Exit Ticket

After Timeline Individual, ask students to complete a slip with: 1. Define 'customary international law' in their own words. 2. Provide one example of a treaty that codified a customary practice. 3. State one reason why enforcing international law can be difficult for states.

Quick Check

During the Mock UN Treaty Negotiation, present students with two scenarios: Scenario A describes a formal agreement signed by 50 countries, while Scenario B describes a practice followed by most countries for centuries, such as diplomatic immunity. Ask students to identify which is an example of a treaty and which is customary international law, and to briefly explain their reasoning for each.

Extensions & Scaffolding

• Challenge: Ask early finishers to draft a mock treaty article that codifies a customary practice, including enforcement mechanisms.
• Scaffolding: For struggling students, provide partially completed timelines with key dates and events to scaffold their research.
• Deeper exploration: Invite students to research a real-world example of a treaty that failed to gain universal ratification and analyze why customary law filled the gap.

Key Vocabulary

Treaty	A formal, legally binding written agreement between two or more sovereign states, or between states and international organizations. Treaties are a primary source of international law, outlining rights and obligations.
Customary International Law	Law that arises from the consistent and general practice of states, accepted as law. It is unwritten and based on the principle that states follow certain practices out of a sense of legal obligation.
State Sovereignty	The supreme authority of a state within its territory, free from external control. It is a fundamental principle in international law, often creating tension with international legal obligations.
Jus Cogens	Peremptory norms of general international law from which no derogation is permitted. These are fundamental principles that bind all states, such as the prohibition of genocide or torture.
Ratification	The formal act by which a state confirms its consent to be bound by a treaty. This process typically involves domestic legislative approval before the treaty enters into force for that state.