The continental shelf is a term that most often appears in the media in connection with oil and gas extraction, or debates about mining minerals from the deep seabed. In practice, it is both a legal and a geological concept that determines who may explore and exploit the mineral wealth of the seabed and subsoil. Without clear rules, there would be a risk of disputes, environmental damage, and uncertainty for states and companies alike. The overview below explains the key concepts, rules, and practice under international law of the sea.
What the continental shelf is (and why it differs from the exclusive economic zone)
From a legal perspective, it means the “seabed and subsoil” as the natural prolongation of a country’s land territory under the sea, over which the coastal state has sovereign rights for the purpose of exploring and exploiting mineral resources. These rights exist “ipso facto and ab initio”—automatically and without any need for a formal declaration. In everyday language, the shelf is often confused with the exclusive economic zone (EEZ), but they are not the same: the EEZ primarily concerns the water column (fisheries, energy from water and wind), whereas the continental shelf concerns only the seabed and subsoil (oil, gas, minerals). The core definition and states’ rights are set out in the United Nations Convention on the Law of the Sea (UNCLOS), especially Article 76 and the provisions that follow.
How the outer limits of the continental shelf are determined
Every coastal state has a “legal” continental shelf out to at least 200 nautical miles (nm) from the baselines, even if the geological edge of the continent extends a shorter distance. However, if the geological continental margin extends farther, the shelf may continue beyond 200 nm—typically up to a maximum of 350 nm, or up to 100 nm beyond the 2,500-metre isobath, under the technical rules of Article 76. To demonstrate how far such an extended shelf reaches, states submit scientific data to an intergovernmental body called the Commission on the Limits of the Continental Shelf (CLCS), which issues recommendations on the outer limits.
The role of the Commission on the Limits of the Continental Shelf (CLCS)
The CLCS does not delimit boundaries between states—it assesses only whether the scientific and technical data submitted justify a single state’s outer shelf limits seaward, toward the high seas. The Commission follows its own rules of procedure, evaluates sediment thickness and morphological and geophysical criteria, and then issues recommendations. A state that establishes its limits “on the basis of the recommendations” gains strong legal certainty vis-à-vis other states that its outer continental shelf boundary complies with UNCLOS.
Where national jurisdiction ends: “the Area” and international protection
Beyond the outer limits of national shelves lies “the Area”—the seabed and subsoil beyond national jurisdiction. There, resources do not belong to individual states; they are the “common heritage of mankind,” and their exploration and potential exploitation are subject to the rules and oversight of the International Seabed Authority (ISA). The ISA adopts the so-called Mining Code—regulations for exploration and (in future) exploitation, which are also intended to ensure effective protection of the marine environment. Commercial mining in “the Area” is still in preparation, and the debate over environmental risks remains intense.
How shelves are divided between neighbours: from “equidistance” to an “equitable solution”
If two neighbouring states have overlapping claims, the boundary is determined by agreement, based on international law and case law. A turning point was the North Sea Continental Shelf Cases (1969), in which the International Court of Justice rejected a strictly automatic “equidistance” rule and stressed the need to achieve an “equitable result” in light of coastal specificities (e.g., concave coastlines). Modern practice therefore typically uses an equidistance line adjusted for relevant circumstances, so that the final line is not disproportionately unfair.
What rights a state has over its continental shelf
The coastal state has exclusive rights to explore and exploit the mineral resources of the seabed and subsoil, such as oil, gas, or solid minerals. It may authorize drilling, build artificial islands or installations, and regulate cables and pipelines, while having to respect certain freedoms of other states (for example, the laying of submarine cables). These rights apply without the state having to “occupy” or “use” the shelf. The foundation is set directly by UNCLOS (Part VI), which also provides, in general terms, for the duty to protect and preserve the marine environment.
What the world would look like without today’s continental shelf regime
Without the UNCLOS rules, companies and states would find themselves in a legal vacuum. Investments in exploration would be risky, insurers would avoid projects, and disputes would escalate because there would be no shared language or institutions for resolving conflicts. In “the Area,” without an authority like the ISA, there would be a risk of a “race to the bottom,” with everyone trying to extract as much as possible regardless of long-term consequences. Such a situation would increase the risk of overlapping claims, habitat destruction, and cumulative damage that is very difficult to remedy in the deep ocean. Today’s regime is not perfect, but it provides a minimum framework of legal certainty, transparency, and environmental safeguards.
Common myths: the shelf is not about fish, and 200 nm is not a “ceiling”
A common misconception is that “shelf = fishing.” Fishing and energy from the water column fall within EEZ competences, while the shelf concerns the seabed and subsoil. It is also not true that 200 nm is always the final limit—if the geological edge of the continent extends beyond 200 nm, a state may have an extended shelf if it substantiates this with data and the CLCS issues a favourable recommendation. Conversely, where neighbours are close, the boundary may be shorter and requires agreement or a court decision.
Sources
- United Nations – United Nations Convention on the Law of the Sea (UNCLOS) – full text (Arts. 2, 55–57, 76, 77): https://treaties.un.org/doc/publication/CTC/Ch_XXI_6_english_p.pdf
- UN DOALOS – Introduction to the Law of the Sea (territorial sea 12 NM, contiguous zone 24 NM, EEZ 200 NM): https://www.un.org/depts/los/LEGISLATIONANDTREATIES/introduction.htm
- International Court of Justice – North Sea Continental Shelf Cases (1969) – Summaries/Judgment: https://www.icj-cij.org/case/52/summaries
- International Seabed Authority – Frequently Asked Questions (mandate over “the Area,” common heritage of mankind): https://isa.org.jm/frequently-asked-questions-faqs/
Jana
I like turning curiosity into words, and writing articles is my way of capturing ideas before they slip away — and sharing them with anyone who feels like reading.
