1. Introduction

The international law of offshore electricity systems concerns the legal rules governing electricity infrastructure located in, constructed across, or connected through maritime areas beyond the territorial land territory of a State. It has become increasingly important because offshore wind farms, submarine electricity cables, offshore substations, hybrid interconnectors, and energy islands are expanding rapidly.

Offshore electricity systems are legally complex because they operate at the intersection of several fields of international law, including:

the United Nations Convention on the Law of the Sea (UNCLOS);

international environmental law;

international energy and investment law;

maritime safety and navigation law;

State responsibility;

international arbitration;

regional electricity-market rules; and

bilateral and multilateral agreements concerning submarine cables and electricity interconnection.

There is no single comprehensive international treaty dealing exclusively with offshore electricity systems. Instead, their legal framework is derived from several overlapping regimes.

2. Meaning and Scope

An offshore electricity system may include:

Offshore wind turbines and foundations;

offshore solar installations;

offshore substations;

submarine electricity cables;

electricity interconnectors between States;

hybrid offshore energy projects combining generation and interconnection;

artificial islands or energy islands;

offshore storage facilities;

offshore hydrogen-electricity infrastructure; and

associated monitoring, maintenance and navigation infrastructure.

The applicable legal regime depends heavily upon the maritime zone in which the infrastructure is located.

3. Maritime Zones and Offshore Electricity Infrastructure

UNCLOS divides maritime jurisdiction into different zones, and the legal rights of States differ substantially between them.

A. Territorial Sea

A coastal State generally exercises sovereignty over its territorial sea, extending up to 12 nautical miles from its baselines.

Consequently, offshore electricity installations situated in the territorial sea are subject to extensive coastal-State jurisdiction.

The State can regulate:

construction;

environmental protection;

navigation;

safety zones;

cables;

licensing;

electricity generation; and

decommissioning.

However, the coastal State must also respect the international legal regime governing innocent passage.

B. Exclusive Economic Zone

The EEZ may extend up to 200 nautical miles.

The coastal State does not possess full sovereignty over the EEZ. Instead, it possesses sovereign rights concerning natural resources and jurisdiction over specified matters.

UNCLOS Article 56 is particularly important because it gives the coastal State rights relating to:

exploration;

exploitation;

conservation;

management of natural resources; and

certain artificial islands, installations and structures.

Offshore wind development is therefore closely connected to Article 56.

C. Continental Shelf

The continental shelf regime is especially important for offshore renewable-energy infrastructure.

Under UNCLOS, coastal States possess sovereign rights over the continental shelf for exploring and exploiting its natural resources.

However, those rights do not amount to unlimited sovereignty over all activities occurring on the seabed.

This creates an important legal distinction between:

resource exploitation and electricity infrastructure development.

4. Offshore Wind Farms Under International Law

Offshore wind farms are generally regulated through a combination of domestic licensing and international maritime law.

A typical project may involve:

Wind turbines → offshore substation → submarine cable → national transmission network.

International law becomes particularly important where:

the wind farm lies in an EEZ;

cables cross international maritime boundaries;

a project is located near another State;

electricity is transmitted internationally;

environmental impacts cross borders; or

several States share a marine ecosystem.

UNCLOS Article 60 permits coastal States to establish artificial islands, installations and structures in the EEZ, subject to the Convention.

The coastal State also has jurisdiction concerning:

customs;

fiscal matters;

health;

safety; and

immigration laws connected with the installation.

5. Submarine Electricity Cables

Submarine electricity cables are one of the most important elements of offshore electricity systems.

International law traditionally distinguishes between:

territorial seas;

EEZs;

continental shelves; and

the high seas.

UNCLOS recognizes important freedoms concerning submarine cables.

Article 58

Other States enjoy certain freedoms in the EEZ, including freedoms related to laying submarine cables and pipelines.

This produces a potential conflict:

Coastal-State interests vs. cable-laying freedoms of other States.

The coastal State may regulate certain activities, but it cannot simply treat the entire EEZ as equivalent to territorial sovereignty.

6. Article 79 and Submarine Cables

UNCLOS Article 79 provides an important legal basis for submarine cables and pipelines on the continental shelf.

States have the right to lay submarine cables and pipelines on the continental shelf, subject to specified conditions.

The coastal State cannot normally prevent the laying of cables merely because the seabed falls within its continental shelf.

However, the precise course of a cable on the continental shelf is subject to the consent of the coastal State.

This distinction is critical:

The right to lay cables does not necessarily mean an unrestricted right to choose their exact route.

7. Protection of Submarine Electricity Cables

International law also recognizes obligations concerning damage to submarine cables.

The traditional legal framework can be traced to the 1884 Convention for the Protection of Submarine Telegraph Cables.

Although originally designed for telecommunication cables, the principles illustrate the longstanding international concern with protecting submarine cable infrastructure.

Modern electricity interconnectors create similar concerns because intentional or negligent damage can cause:

electricity outages;

market disruption;

grid instability;

financial losses; and

potentially wider energy-security consequences.

8. Environmental Impact Assessment

Environmental law is a central component of offshore electricity regulation.

Large offshore electricity projects may affect:

marine mammals;

fish;

seabirds;

fisheries;

marine habitats;

sediment;

coastal ecosystems;

navigation; and

neighboring States.

International law increasingly requires States to consider environmental impacts before authorizing major projects.

The principle of environmental impact assessment (EIA) has been recognized in international jurisprudence.

A particularly important authority is:

Pulp Mills on the River Uruguay (Argentina v Uruguay), ICJ, 2010

The International Court of Justice recognized the importance of conducting an environmental impact assessment where there is a risk that a proposed industrial activity may have significant adverse transboundary environmental effects.

Although the dispute concerned a river rather than offshore electricity, its reasoning is relevant to major offshore infrastructure where significant transboundary environmental harm is reasonably foreseeable.

9. The MOX Plant Case

Ireland v United Kingdom — MOX Plant

The dispute concerning the MOX nuclear facility at Sellafield raised issues concerning environmental protection and marine pollution.

The proceedings before international tribunals involved questions concerning:

marine environmental protection;

information exchange;

cooperation; and

obligations under the law of the sea.

The case illustrates that energy infrastructure can generate international disputes even where the infrastructure itself is located within the territory or jurisdiction of one State.

10. ITLOS and Marine Environmental Protection

The International Tribunal for the Law of the Sea has emphasized the obligation of States to cooperate in protecting the marine environment.

Responsibilities and Obligations of States Sponsoring Persons and Entities with Respect to Activities in the Area, ITLOS Seabed Disputes Chamber, 2011

The Chamber emphasized principles concerning:

due diligence;

environmental protection;

precaution;

cooperation; and

responsibility in relation to activities affecting the marine environment.

Although the advisory opinion concerned activities in the international seabed area rather than offshore wind farms, it provides important principles for understanding environmental responsibilities associated with offshore infrastructure.

11. The Pulp Mills Principle and Offshore Electricity

For an offshore electricity project with potentially significant transboundary effects, international law may require the State to undertake appropriate environmental assessment.

For example:

State A

→ constructs offshore wind farm

→ underwater noise and ecological effects

→ migratory marine species

→ effects potentially reaching State B

The international legal issue becomes whether State A adequately assessed and managed foreseeable transboundary environmental effects.

Thus, environmental assessment is not merely a domestic administrative procedure. Under certain circumstances, it can become an obligation under international law.

12. Duty to Cooperate

International law increasingly emphasizes cooperation where activities affect shared or interconnected marine environments.

Cooperation may involve:

exchange of scientific information;

environmental monitoring;

notification;

consultation;

joint impact assessment;

emergency response;

cable-route coordination; and

fisheries management.

For offshore electricity systems located near maritime boundaries, cooperation can reduce conflicts between:

energy generation;

fishing;

shipping;

environmental conservation;

defence;

telecommunications; and

other seabed uses.

13. Navigation and Safety

Offshore electricity installations can interfere with maritime navigation.

A wind farm may occupy a substantial marine area and therefore create issues concerning:

shipping lanes;

navigational safety;

search and rescue;

emergency access;

vessel collision;

military operations; and

safety zones.

UNCLOS Article 60 permits coastal States to establish reasonable safety zones around installations and structures in the EEZ.

However, those zones must respect international navigation rights.

14. Artificial Islands and Energy Islands

Future electricity systems may use large energy islands or artificial islands to connect offshore wind farms to several national electricity grids.

These projects raise important questions:

Who has jurisdiction over an energy island?

Can an artificial island generate territorial sovereignty?

Which State regulates the electricity market?

What happens if the island connects three or more countries?

Which environmental law applies?

Who is responsible for accidents?

UNCLOS provides that artificial islands, installations and structures do not possess the status of islands.

They therefore do not generate their own territorial sea.

This is important because constructing offshore electricity infrastructure cannot ordinarily be used as a means of creating new maritime territory.

15. Cross-Border Electricity Interconnectors

An offshore electricity system may also function as an international interconnector.

For example:

Offshore wind farm

↓

Subsea cable

↓

State A grid

↕

State B grid

Such projects require coordination concerning:

technical standards;

grid stability;

capacity allocation;

transmission charges;

ownership;

emergency procedures;

electricity trading;

maintenance;

liability; and

dispute settlement.

International agreements are therefore frequently required in addition to UNCLOS.

16. International Investment Law

Offshore electricity projects frequently require substantial foreign investment.

Investors may seek protection under:

bilateral investment treaties;

multilateral investment agreements;

investment contracts; and

domestic investment legislation.

Possible disputes can involve:

cancellation of offshore leases;

changes in subsidies;

tariff reductions;

discriminatory treatment;

expropriation;

permit withdrawal;

regulatory changes; and

environmental restrictions.

17. Energy Charter Treaty Arbitration

The Energy Charter Treaty (ECT) historically played an important role in international energy investment disputes.

Energy-sector investors have brought claims concerning regulatory measures affecting energy investments.

However, the ECT framework has undergone major political and legal changes, particularly concerning its application within the European Union.

Therefore, its relevance to modern offshore electricity investment disputes must be assessed according to:

the date of the investment;

the States involved;

applicable treaty provisions;

EU law where relevant; and

any withdrawal or sunset provisions.

18. Case Law: Electrabel v Hungary

Electrabel S.A. v Hungary

This investment arbitration concerned the electricity sector and regulatory changes affecting an investor.

The tribunal examined issues involving:

regulatory measures;

legitimate expectations;

investment protection;

EU electricity-market developments; and

the relationship between international investment law and regulatory authority.

The case demonstrates an important principle for offshore electricity projects:

Investors may have treaty protections, but States generally retain regulatory authority to pursue legitimate public objectives.

This is particularly relevant where environmental or electricity-market regulation changes during the life of a long-term offshore project.

19. Renewable-Energy Disputes

Offshore renewable projects may also generate disputes involving government support mechanisms.

Renewable-energy investments can depend upon:

feed-in tariffs;

contracts for difference;

renewable-energy certificates;

tax incentives;

auctions;

grid-connection guarantees; and

long-term PPAs.

Changes to these arrangements can produce investment disputes.

Cases involving renewable-energy regulation in Europe, including Charanne v Spain and subsequent Spanish renewable-energy arbitrations, illustrate how tribunals have approached claims arising from regulatory changes.

However, each case depends on its specific treaty, factual circumstances and applicable law.

20. International Environmental Law and State Responsibility

If an offshore electricity project causes significant environmental damage, questions of State responsibility may arise.

The basic structure is:

conduct attributable to the State;

breach of an international obligation;

resulting legal consequences.

International law also distinguishes between:

State responsibility;

private operator liability; and

contractual liability.

For example, if a privately owned offshore wind farm damages another State's marine environment, the legal responsibility of the operator and the international responsibility of the State that authorized or failed to regulate the activity may involve different legal questions.

21. Transboundary Harm

A fundamental principle of international environmental law is that States should not knowingly allow activities within their jurisdiction to cause significant environmental harm to other States or areas beyond national jurisdiction.

This principle has appeared in international jurisprudence and environmental declarations.

The Trail Smelter Arbitration is a classic authority concerning transboundary pollution.

Although it involved air pollution rather than electricity infrastructure, it established an influential principle concerning cross-border environmental harm.

Its reasoning can be relevant when offshore electricity activities generate significant transboundary effects.

22. Gabčíkovo-Nagymaros Project

Hungary v Slovakia, ICJ, 1997

The case concerned a major hydroelectric project and raised issues involving:

environmental protection;

sustainable development;

treaty obligations;

necessity; and

changing environmental circumstances.

The judgment is relevant to energy infrastructure because it demonstrates that energy-development treaties cannot necessarily be considered in isolation from evolving environmental concerns.

For offshore electricity projects, this reinforces the importance of integrating energy development with environmental obligations.

23. Climate Change and Offshore Electricity

Offshore renewable electricity is closely connected to international climate law.

The Paris Agreement establishes a framework for States to reduce greenhouse-gas emissions and strengthen climate action.

However, the Paris Agreement does not establish a detailed international licensing system for offshore wind farms.

Instead, States implement climate commitments primarily through domestic policies and regulatory frameworks.

International climate obligations can nevertheless influence:

energy planning;

renewable-energy deployment;

investment decisions;

environmental regulation; and

electricity infrastructure development.

24. Regional Cooperation

Regional organizations have developed more detailed systems for offshore electricity.

The European Union provides an important example.

EU law regulates areas including:

electricity markets;

cross-border transmission;

renewable energy;

maritime spatial planning;

environmental assessment; and

grid interconnection.

The North Sea is particularly significant because several States are developing interconnected offshore wind systems.

This demonstrates how regional law can provide greater regulatory detail than general international law.

25. Maritime Spatial Planning

Offshore electricity infrastructure competes for marine space with:

shipping;

fisheries;

conservation;

defence;

telecommunications;

oil and gas;

tourism; and

other activities.

International and regional law increasingly recognizes the importance of integrated marine spatial planning.

For offshore electricity systems, spatial planning can determine:

turbine locations;

cable corridors;

landing points;

interconnector routes;

environmental exclusion zones; and

navigation corridors.

26. Offshore Electricity and Fisheries

Offshore wind farms may conflict with fishing activities.

Potential disputes concern:

exclusion zones;

access to fishing grounds;

cable corridors;

construction periods;

electromagnetic effects;

seabed disturbance; and

compensation.

International law therefore requires offshore electricity development to be coordinated with existing maritime uses.

The legal solution often involves a combination of:

licensing + consultation + environmental assessment + maritime spatial planning + compensation mechanisms.

27. Cybersecurity of Offshore Electricity Systems

Modern offshore electricity infrastructure increasingly depends upon:

digital control systems;

remote monitoring;

automated substations;

SCADA systems;

satellite communications; and

interconnected national grids.

A cyberattack against an offshore electricity system could have cross-border consequences.

International law does not yet provide a comprehensive offshore-energy cybersecurity treaty.

Nevertheless, cybersecurity may increasingly be addressed through:

national critical-infrastructure legislation;

regional electricity-security rules;

international cooperation;

incident reporting;

maritime security arrangements; and

general international law governing harmful cyber operations.

28. Dispute Settlement

Offshore electricity disputes can be resolved through several mechanisms.

1. Domestic courts

Questions concerning permits, environmental approvals and domestic electricity regulation may be determined by national courts.

2. International arbitration

Investment treaties and commercial contracts may provide for arbitration.

3. ITLOS

Certain disputes concerning interpretation and application of UNCLOS may fall within the jurisdiction of the International Tribunal for the Law of the Sea.

4. International Court of Justice

States may submit disputes to the ICJ where jurisdiction exists.

5. Treaty-specific mechanisms

Regional agreements may establish specialized dispute-resolution procedures.

29. Important Case Laws

30. Key Legal Principles

The international law of offshore electricity systems can therefore be understood through several core principles.

Principle 1: Coastal-State jurisdiction

Coastal States possess substantial authority over offshore infrastructure within their territorial sea and specified jurisdictional rights in the EEZ and continental shelf.

Principle 2: Freedom of submarine cables

International law protects important rights relating to submarine cables, particularly beyond the territorial sea.

Principle 3: Environmental protection

Offshore electricity development must comply with applicable international environmental obligations.

Principle 4: Environmental impact assessment

Projects capable of causing significant environmental effects may require appropriate environmental assessment.

Principle 5: Cooperation

States should cooperate where offshore activities may affect shared marine environments or neighboring States.

Principle 6: Navigation

Offshore installations must be developed consistently with maritime navigation and safety obligations.

Principle 7: Investment protection

Foreign investors may receive protection under applicable investment treaties, although States retain regulatory powers.

Principle 8: Sustainable development

Energy security, renewable-energy development and environmental protection increasingly have to be considered together.

31. Major Legal Challenges for the Future

The rapid development of offshore electricity systems creates several unresolved legal questions.

A. Multi-State offshore grids

If one offshore wind complex supplies several States, determining jurisdiction becomes increasingly complicated.

B. Energy islands

Artificial energy islands create novel questions regarding jurisdiction, environmental responsibility and regulatory authority.

C. Hybrid interconnectors

A single cable may function both as an electricity transmission interconnector and as an export connection from an offshore wind farm.

D. Cross-border environmental impacts

Large offshore projects can affect marine ecosystems extending across national maritime boundaries.

E. Decommissioning

International law has comparatively less developed rules concerning the removal of obsolete offshore electricity infrastructure.

F. Cybersecurity

Cross-border electricity infrastructure creates shared cybersecurity vulnerabilities.

G. Climate change

Rising sea levels, extreme weather and changing marine conditions may create new risks for offshore infrastructure.

32. Conclusion

The international law of offshore electricity systems is not governed by one unified legal instrument. Instead, it consists of an interconnected framework based principally on UNCLOS, international environmental law, investment law, maritime law, regional electricity regulation and bilateral or multilateral agreements.

UNCLOS establishes the fundamental jurisdictional structure for offshore infrastructure, while environmental law imposes obligations concerning marine protection, assessment and cooperation. Investment law protects qualifying foreign investments, while regional electricity regimes increasingly regulate cross-border electricity trading and grid integration.

The jurisprudence of the ICJ, ITLOS and investment tribunals demonstrates that offshore electricity development must balance several interests simultaneously: energy security, renewable-energy development, freedom of navigation, coastal-State jurisdiction, environmental protection, investment protection and international cooperation.

The future development of offshore wind, submarine interconnectors and multi-State offshore grids will therefore require increasingly sophisticated international legal arrangements. In particular, hybrid interconnectors, energy islands, shared offshore grids and transboundary environmental effects are likely to become central issues in the future evolution of international energy and maritime law.