Introduction

Electricity interconnectors are transmission facilities that connect the electricity systems of two or more jurisdictions. When these facilities cross seas or oceans, their development and operation become subject not only to energy and electricity regulation but also to international maritime law. Submarine electricity cables may pass through territorial seas, exclusive economic zones (EEZs), continental shelves, straits, and areas beyond national jurisdiction. Consequently, questions concerning jurisdiction, cable laying, environmental protection, navigation, fisheries, offshore construction, maintenance, liability, and dispute settlement arise at the intersection of international energy law and the law of the sea.

The principal international legal framework is the United Nations Convention on the Law of the Sea (UNCLOS), supplemented by customary international law, regional agreements, bilateral interconnector treaties, environmental conventions, national offshore legislation, and electricity-market rules.

1. Meaning and Nature of Electricity Interconnectors

An electricity interconnector normally consists of high-voltage transmission cables linking electricity grids across a national boundary. Where the boundary is maritime, the connection generally requires submarine cables.

Examples include:

electricity cables between neighbouring coastal states;

offshore wind connections linking offshore generation to national grids;

hybrid interconnectors combining electricity trading and offshore renewable generation;

subsea cables crossing EEZs or continental shelves;

electricity links passing through international straits.

An interconnector therefore has a dual legal character. It is simultaneously:

an energy infrastructure asset;

a submarine cable infrastructure project.

The second characteristic brings it within important rules of international maritime law.

2. UNCLOS as the Principal Legal Framework

The most important treaty is the 1982 United Nations Convention on the Law of the Sea.

UNCLOS establishes different maritime zones, and the legal rights concerning submarine electricity cables vary according to the zone through which an interconnector passes.

The principal zones are:

internal waters;

territorial sea;

contiguous zone;

EEZ;

continental shelf;

high seas;

the international seabed Area.

The legal status of a submarine cable therefore depends substantially on its geographical location.

3. Submarine Cables and the Territorial Sea

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

This sovereignty covers the seabed and subsoil as well as the waters above them.

However, foreign ships enjoy the right of innocent passage, subject to UNCLOS.

For electricity interconnectors, this creates an important distinction.

A state may regulate activities associated with cable construction and maintenance within its territorial sea, but the existence of international maritime rights means that coastal-state authority is not unlimited.

The coastal state can regulate matters such as:

cable-laying operations;

offshore construction;

environmental protection;

navigational safety;

protection of marine infrastructure;

pollution prevention;

permits and construction zones.

An interconnector project crossing another state's territorial sea will therefore ordinarily require substantial cooperation with that coastal state.

4. Freedom to Lay Submarine Cables

One of the central principles of international maritime law is the recognition of the right to lay submarine cables.

UNCLOS Article 79 is particularly important concerning submarine cables and pipelines on the continental shelf.

Article 79 provides that:

"All States are entitled to lay submarine cables and pipelines on the continental shelf."

This is highly significant for electricity interconnectors because submarine electricity cables fall within the broader category of submarine cables.

However, this freedom is not absolute.

The coastal state retains important rights concerning:

exploration and exploitation of natural resources;

protection of the marine environment;

reasonable measures for preventing, reducing and controlling pollution;

routing of pipelines;

activities associated with resource exploitation.

Thus, international maritime law attempts to balance two interests:

Coastal-state sovereign rights + international freedom of submarine cable infrastructure.

5. Continental Shelf Jurisdiction

The continental shelf regime is particularly important for submarine electricity interconnectors.

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

These rights are different from full sovereignty over the territorial sea.

Consequently, a coastal state cannot simply treat every submarine cable crossing its continental shelf as though the cable were located on national land.

Article 79 recognizes the right of other states to lay submarine cables while simultaneously preserving coastal-state rights.

This distinction is fundamental for international electricity infrastructure.

6. EEZ and Electricity Interconnectors

The EEZ can extend up to 200 nautical miles from the coastal state's baselines.

Within the EEZ, the coastal state has sovereign rights concerning natural resources and jurisdiction over specified matters.

At the same time, other states retain important freedoms, including freedoms associated with navigation and submarine cables.

Therefore, an electricity interconnector crossing an EEZ normally exists within a complex jurisdictional environment.

The coastal state may regulate:

offshore installations;

environmental protection;

marine scientific research;

resource-related activities;

safety measures.

But it must also respect internationally recognized rights relating to submarine cables and navigation.

7. Article 79 and the Routing of Interconnectors

Article 79(3) provides that the delineation of the course for laying pipelines on the continental shelf is subject to the consent of the coastal state.

For submarine cables, the position is more permissive.

This creates an important legal distinction between pipelines and cables.

An electricity interconnector developer must therefore examine:

the exact maritime zone;

whether the cable crosses resource-exploitation areas;

whether offshore installations are present;

environmental restrictions;

navigation requirements;

national permitting requirements.

The practical consequence is that the international legal right to lay a cable does not eliminate the need for regulatory coordination.

8. Protection of Existing Submarine Cables

UNCLOS also contains provisions concerning the protection of submarine cables.

States must have regard to existing cables when laying new infrastructure.

This becomes particularly important as offshore energy infrastructure expands.

The seabed increasingly contains:

telecommunications cables;

electricity interconnectors;

offshore wind export cables;

pipelines;

oil and gas infrastructure;

carbon-storage infrastructure.

The possibility of interference or accidental damage therefore creates significant legal and operational risks.

9. Liability for Damage to Cables

International maritime law also addresses responsibility for damage to submarine cables.

The historical foundation can be traced to the 1884 Convention for the Protection of Submarine Telegraph Cables.

The principles developed under this regime remain relevant to modern submarine cable infrastructure, although electricity interconnectors obviously involve technologies far more sophisticated than nineteenth-century telegraph cables.

Potential liability may arise from:

vessel anchoring;

fishing operations;

dredging;

construction activities;

offshore energy development;

negligent cable installation;

intentional interference.

Modern interconnector agreements therefore commonly contain detailed provisions on:

liability;

indemnification;

repair costs;

emergency response;

cable burial;

exclusion zones;

notification procedures.

10. Environmental Protection

Environmental law is increasingly important in the construction of submarine electricity interconnectors.

UNCLOS Part XII establishes general obligations concerning the protection and preservation of the marine environment.

States have an obligation to protect the marine environment and to take measures concerning marine pollution.

Interconnector construction can potentially affect:

seabed habitats;

marine mammals;

fish populations;

sediment;

protected marine areas;

archaeological sites;

coastal ecosystems.

Environmental impact assessment can therefore become a central requirement.

11. Environmental Impact Assessment and the ITLOS Advisory Opinion

A particularly important development occurred in the Responsibilities and Obligations of States Sponsoring Persons and Entities with Respect to Activities in the Area Advisory Opinion (2011) of the International Tribunal for the Law of the Sea (ITLOS).

Although the case concerned mineral activities in the international seabed Area rather than electricity interconnectors, the Tribunal emphasized the importance of environmental obligations and due diligence.

The broader principle is highly relevant to offshore electricity infrastructure:

States must exercise appropriate due diligence to prevent environmental harm resulting from activities under their jurisdiction or control.

This supports the development of environmental assessment and monitoring requirements for major submarine cable projects.

12. Transboundary Environmental Effects

An interconnector can affect several jurisdictions simultaneously.

For example:

State A → territorial sea → EEZ → disputed maritime area → State B

Construction may affect ecosystems and maritime activities across borders.

International environmental law consequently encourages:

environmental impact assessment;

information sharing;

consultation;

notification;

cooperation;

monitoring.

The Pulp Mills on the River Uruguay (Argentina v Uruguay) case before the International Court of Justice (ICJ) is important in this context.

The ICJ recognized environmental impact assessment as an important requirement where there is a risk of significant transboundary harm.

Although the case concerned a river rather than a submarine cable, its reasoning has broader relevance to major transboundary infrastructure projects.

13. Maritime Delimitation and Interconnector Routing

Another major legal problem arises when the proposed cable passes through an area where maritime boundaries are disputed.

A state cannot necessarily assume that its preferred cable route will be legally unobjectionable simply because it appears geographically shortest.

Issues can include:

territorial-sea boundaries;

EEZ boundaries;

continental-shelf boundaries;

overlapping claims;

disputed islands;

disputed maritime zones.

An interconnector agreement may therefore need to specify how the parties will deal with boundary uncertainty.

14. Maritime Delimitation Case Law

The North Sea Continental Shelf Cases (Germany v Denmark; Germany v Netherlands) before the ICJ are foundational.

The Court examined principles governing continental-shelf delimitation and emphasized that maritime boundaries should be determined according to equitable principles and relevant circumstances.

The case is important for interconnectors because the location of the continental shelf boundary can influence:

regulatory jurisdiction;

cable routing;

environmental approvals;

offshore construction rights.

15. Black Sea Maritime Delimitation Case

Another important case is Maritime Delimitation in the Black Sea (Romania v Ukraine).

The ICJ developed a structured approach to maritime delimitation, including consideration of relevant geographical circumstances.

For electricity interconnectors, boundary determination can be commercially significant because a cable route may cross multiple maritime jurisdictions.

16. International Straits

Some electricity interconnectors cross international straits.

UNCLOS provides special rules concerning straits used for international navigation.

The transit passage regime protects navigation through qualifying international straits.

This has implications for submarine infrastructure because cable construction must coexist with international navigation.

A state cannot simply obstruct international navigation because an interconnector is being constructed.

Accordingly, projects may require:

navigational warnings;

construction corridors;

temporary exclusion zones;

coordination with maritime authorities;

careful scheduling of cable-laying operations.

17. The Corfu Channel Case

The Corfu Channel (United Kingdom v Albania) case is a foundational international maritime-law decision.

The ICJ recognized the importance of international navigation through straits and considered Albania's responsibilities concerning dangers to navigation.

Although the dispute did not concern electricity cables, the case demonstrates a broader principle:

maritime infrastructure and coastal-state jurisdiction must be exercised consistently with international navigation obligations.

That principle is relevant to interconnector construction in heavily trafficked maritime areas.

18. Offshore Renewable Energy and Hybrid Interconnectors

The legal importance of maritime law is growing because electricity interconnectors are increasingly connected with offshore renewable-energy projects.

A modern project may involve:

Offshore wind farms → submarine export cables → offshore hub → international interconnector → foreign electricity market

Such infrastructure creates overlapping legal regimes involving:

UNCLOS;

electricity-market law;

renewable-energy regulation;

environmental law;

maritime safety;

investment law;

national permitting;

international commercial contracts.

Hybrid interconnectors are therefore legally more complicated than traditional point-to-point electricity cables.

19. Offshore Installations and Safety Zones

Where an interconnector is associated with offshore substations or renewable-energy installations, additional maritime rules become relevant.

States may establish safety measures around offshore installations, subject to applicable international law.

However, safety measures should not unnecessarily interfere with internationally protected navigation rights.

The legal design of offshore exclusion or safety zones therefore requires careful coordination between:

maritime authorities;

energy regulators;

environmental agencies;

electricity system operators;

naval authorities;

cable operators.

20. Fisheries and Interconnector Cables

Fishing is one of the major practical risks to submarine cables.

Bottom trawling, anchoring, dredging and related activities can damage buried or exposed cables.

This creates conflicts between:

electricity infrastructure;

fishing rights;

navigation;

environmental conservation.

Governments may therefore establish cable protection zones or impose restrictions around critical infrastructure.

Such measures must be consistent with the relevant maritime jurisdiction and international obligations.

21. Maritime Archaeology

Submarine cable routes can encounter:

shipwrecks;

archaeological remains;

historic vessels;

cultural heritage sites.

Consequently, interconnector developers may need archaeological surveys before construction.

International and national cultural-heritage rules can impose additional restrictions.

This is another example of why seabed mapping is legally as important as engineering surveys.

22. Security of Electricity Interconnectors

Modern interconnectors are also critical energy-security infrastructure.

Damage may arise from:

accidental vessel activity;

fishing;

sabotage;

deliberate interference;

geopolitical disputes;

underwater construction.

International law does not create one comprehensive treaty exclusively governing the security of electricity interconnectors.

Instead, protection is distributed among:

UNCLOS;

national security legislation;

criminal law;

maritime safety rules;

international cooperation arrangements;

bilateral agreements;

electricity-sector security frameworks.

23. Dispute Settlement

International disputes concerning interconnectors may involve several forms of dispute settlement.

Potential mechanisms include:

(a) Negotiation

States may resolve routing, permitting and operational disputes through diplomatic negotiation.

(b) Arbitration

Interconnector agreements can contain arbitration clauses covering:

construction disputes;

contractual liability;

delays;

damages;

operational obligations.

(c) ITLOS

Where UNCLOS disputes arise and jurisdictional requirements are satisfied, disputes may potentially be submitted to the International Tribunal for the Law of the Sea.

(d) ICJ

States may also submit maritime disputes to the International Court of Justice where jurisdiction exists.

24. International Investment Law

Private companies frequently finance electricity interconnectors.

Investment treaties may therefore become relevant where governmental measures allegedly affect an investment.

Potential disputes can concern:

cancellation of permits;

discriminatory regulation;

expropriation;

regulatory changes;

transmission tariffs;

access to electricity markets.

The interaction between investment protection and a state's regulatory authority over marine and energy infrastructure can be legally complex.

25. Important Case Laws

The following cases are particularly useful when studying international maritime law and electricity interconnectors:

These cases do not all concern electricity interconnectors directly. Their importance lies in the principles of maritime jurisdiction, cable infrastructure, environmental protection, maritime delimitation and dispute settlement that can apply to interconnector projects.

26. Legal Challenges for Future Interconnectors

The expansion of offshore electricity systems will create several new legal challenges.

1. Multi-state projects

A single cable may cross the maritime zones of several states, requiring coordinated legal regimes.

2. Offshore energy hubs

Artificial islands and offshore hubs could connect several electricity markets simultaneously.

3. Hybrid interconnectors

The distinction between electricity transmission infrastructure and offshore generation infrastructure will increasingly become blurred.

4. Cable security

Critical infrastructure protection will become increasingly important.

5. Environmental regulation

Marine biodiversity requirements may impose increasingly detailed obligations on developers.

6. Maritime-space competition

The seabed is becoming increasingly crowded with:

cables;

pipelines;

wind farms;

carbon-storage infrastructure;

shipping routes;

fishing grounds.

This will require more sophisticated marine spatial planning.

Conclusion

International maritime law provides an essential legal foundation for electricity interconnectors crossing maritime areas. UNCLOS is the central framework, particularly its rules concerning submarine cables, continental shelves, EEZs, maritime navigation, environmental protection and dispute settlement.

The fundamental legal balance is between the rights of coastal states to regulate activities within their maritime zones and the international rights associated with submarine cables and navigation.

For modern interconnectors, however, UNCLOS cannot be considered in isolation. Projects increasingly require the combined application of maritime law, environmental law, electricity regulation, investment law, commercial contract law and national offshore legislation.

The case law of the ICJ, ITLOS and arbitral tribunals demonstrates that principles concerning maritime delimitation, environmental due diligence, navigation, cooperation and jurisdiction are central to resolving disputes involving transboundary marine infrastructure. As offshore wind, multinational electricity trading and hybrid interconnectors expand, international maritime law will become an increasingly important component of global electricity governance.