Water covers more than 70% of the planet’s surface. What rules apply in the world’s oceans and seas?
That’s where “freedom of the seas,” a fundamental principle of international law, comes in. It affects everything from trade to travel to national security, and it enables commercial shippers to move peacefully through the Red Sea.
For many thousands of years, we have relied on the ocean for sustenance, commerce, exploration and discovery. The international law of the sea grew out of a need to balance various interests in these areas, including security, commerce and resources.
Isn’t water everywhere treated the same?
No, it isn’t. A well-developed body of international law provides a framework for all claims and activities at sea, and the rules reflect a careful balancing of coastal state and maritime state interests.
Historically, countries made all sorts of claims about the waters along their coastlines and how far out into the ocean they had full sovereignty — in other words, where they could exercise jurisdiction and control in ocean waters much as they did on land.
So what are the rules then?
Many centuries ago, after much debate, and real-world practice of states in their operations at sea, the rule emerged that coastal countries could have sovereign control only in a narrow band of water close to their shoreline, called a “territorial sea.” Beyond that, the “high seas” were declared free for all and belonging to none.
For a long time, territorial seas stretched as far as a state could exercise control from land. That was linked to the distance of a cannon shot fired from shore. This was considered to be about 3 nautical miles (5.6 kilometers). With the negotiation of the 1982 United Nations Law of the Sea Convention, the maximum breadth of a territorial sea claim was extended to 12 nautical miles (22 kilometers).
While a coastal state generally controls its territorial sea, ships of all states enjoy the right of “innocent passage.” All vessels (including military vessels) have the right of innocent passage — they may expeditiously transit the territorial sea as long as they do not engage in certain specified activities deemed to disrupt the peace, good order or security of the coastal state.
In waters beyond the territorial sea, all states enjoy “high seas freedoms” (like the freedoms of navigation and overflight and the laying and maintenance of submarine cables) and other internationally lawful uses of the sea related to these freedoms. In general, that means that ships of any country can exercise those freedoms without interference from any other state. This system of customary international law is reflected in the Law of the Sea Convention.
The Law of the Sea Convention also provides for another important maritime zone: Up to 200 nautical miles (370 kilometers) offshore, a coastal nation can claim an “exclusive economic zone” or EEZ in waters that, until the convention, were deemed to be high seas. In that zone, the country has specific rights and jurisdiction for certain limited purposes, including managing fisheries, producing energy from the water and wind, and protecting and preserving the marine environment.
What happens when two countries’ territorial seas or EEZs overlap each other? The two countries need to agree to a maritime boundary that delimits the countries’ claims.
What happens in waters beyond the territorial sea?
A lot!
About 90,000 commercial vessels transport goods between countries. Also, all countries can lay underwater pipes and cables in waters beyond the territorial sea. Fisheries in EEZs and on the high seas are also important.
Sometimes, countries make excessive maritime claims that attempt to unlawfully restrict access to or use of the seas.
The United States protests excessive maritime claims and conducts freedom of navigation operations — sending a naval ship through waters to assert navigational rights — on a principled basis regardless of the coastal state, including to protest excessive claims by allies and partners.
What about attacks at sea?
Attacks at sea can cause great harm to people and international commerce. They can prevent delivery of food, medicine and humanitarian assistance, raise the cost of energy and consumer goods, and endanger ships’ crews.
In response to recent Houthi attacks on ships in the Red Sea and the Gulf of Aden, some ships have avoided these waters and traveled south, around Africa’s Cape of Good Hope. The United States and the U.K. have imposed sanctions against Houthi military officers responsible, and the United Nations Security Council condemned the attacks and called for “respect for the exercise of navigational rights and freedoms by merchant and commercial vessels.”
Staff writer David Reynolds contributed to this article. An earlier version was published May 19, 2021.