IB Diploma Environmental Systems & Societies HL · Environmental Law
Mini-Lesson
Environmental Law
This is one of the three HL lenses — perspectives that HL students use to analyse every environmental issue. This mini-lesson covers the sources and principles of environmental law (polluter pays, the precautionary principle, intergenerational equity), the difference between hard and soft and national and international law, the tragedy of the commons that law tries to solve, the instruments used (command-and-control vs market-based), key treaties, and environmental justice.
HL lens: law asks not just what is happening to the environment, but who is responsible, who should pay, and how rules can be enforced across sovereign nations.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you're ready.
Law · foundations
What environmental law is, and where it comes from
Environmental law is the body of rules governing how humans interact with the natural world. Its sources include:
National legislation — statutes passed by governments (e.g. clean air acts, protected-area laws).
International treaties and conventions — binding agreements between states (e.g. the Montreal Protocol).
Common law — court judgments, e.g. liability for causing a nuisance or pollution.
Soft law — non-binding declarations, guidelines and codes (e.g. the Rio Declaration) that shape norms.
Hard law creates enforceable obligations; soft law guides behaviour but carries no legal penalty.
Quick check
Hard or soft law?
?A UN summit issues a non-binding declaration of principles that governments are encouraged, but not legally required, to follow. This is an example of...
Law · principles
Key principles of environmental law
Polluter pays principle (PPP) — those who cause pollution should bear the cost of managing it.
Precautionary principle — where an action risks serious or irreversible harm, lack of full scientific certainty should not delay preventive measures.
Sustainable development — meeting present needs without compromising future generations.
Intergenerational equity — fairness to people not yet born.
Common but differentiated responsibilities (CBDR) — all nations share duties, but wealthier, higher-emitting nations should do more.
Quick check
Who pays for the mess?
?A chemical plant must fund the clean-up of a river it contaminated. Which principle of environmental law does this apply?
Calculate
Your turn — polluter pays
1Under a carbon charge of $30 per tonne, a factory that emits 20 000 tonnes of CO₂ a year must pay for its emissions. Calculate the annual charge.
$
Hint: charge = emissions × price = 20 000 × 30.
Quick check
Acting under uncertainty
?Scientists suspect a new pesticide may cause irreversible harm to pollinators, but cannot yet prove it. A government restricts it anyway. Which principle justifies this?
Law · the enforcement gap
International law and the problem of enforcement
The environment ignores borders, but law mostly stops at them. International environmental law faces a structural weakness:
Sovereignty — states cannot easily be forced to act against their will.
No global enforcer — there is no world police or court with automatic power to punish breaches.
Ratification and compliance — treaties bind only the nations that sign and honour them.
This is why treaties rely on incentives, monitoring, funding and peer pressure as much as on legal penalties.
Calculate
Your turn — ratifying a treaty
2Of 50 nations invited to sign an environmental treaty, 45 ratify it. Calculate the percentage of invited nations that ratified.
%
Hint: (45 ÷ 50) × 100.
Law · the commons
The tragedy of the commons
The tragedy of the commons explains why shared resources with no ownership — the atmosphere, oceans, fisheries — get over-exploited: each user gains from taking more, while the cost of depletion is shared by all. Individually rational choices lead to collective ruin.
Environmental law is one answer: it can assign rights, set enforceable limits, or put a price on use so that the shared cost is felt by each user.
Law · instruments
Command-and-control vs market-based instruments
Command-and-control — the state sets legal rules: emission limits, bans, standards and licences, enforced by inspection and penalties. Certain, but can be rigid and costly.
Market-based instruments — use economic incentives: carbon taxes, tradable pollution permits (cap-and-trade), subsidies for clean technology. Flexible and cost-efficient, but rely on correct pricing.
Sort it
Sort the legal tools
Tap a tool, then tap the category it belongs to.
⚖️ Command-and-control
💱 Market-based
📜 Guiding principle
Calculate
Your turn — tightening a cap
3A cap-and-trade scheme cuts a firm’s free emission allowance from 10 000 tonnes to 7500 tonnes of CO₂. Calculate the percentage reduction in its allowance.
Montreal Protocol (1987) — phased out ozone-depleting substances; the most successful environmental treaty.
CITES — regulates international trade in endangered species.
Convention on Biological Diversity (CBD) — conserves biodiversity and shares its benefits.
Paris Agreement (2015) — nations pledge to limit global warming.
Basel Convention — controls transboundary movement of hazardous waste.
Quick check
Matching the treaty
?Which international agreement is designed to regulate and restrict the international trade in endangered plants and animals?
Law · justice
Environmental justice and the rights of nature
Environmental justice concerns the fair distribution of environmental benefits and burdens. Too often, pollution and climate impacts fall hardest on poor communities and nations that did least to cause them.
A newer movement grants legal rights to nature itself — rivers (the Whanganui in New Zealand), forests and ecosystems have been given legal personhood so that guardians can defend them in court.
Quick check
Whose burden?
?Environmental justice is concerned mainly with which of the following?
Match it
Match the environmental-law terms
Tap a statement on the left, then its matching answer on the right.
Statement
Answer
Recap
The big ideas to know
Sources: national legislation, international treaties, common law and soft law; hard vs soft law