And why does it matter?
In theory, everybody owns the seas, and the water, fish, and other material - specifically natural resources, e.g. oil - in or under them (there are separate rules for old pirate ship treasure, though). For the most part, the oceans are what is called a “global common”. There are a couple of others (three more, to be precise: the atmosphere, outer space, and Antarctica; and some people start thinking about cyberspace as well). Commons (also common goods or public goods) are called so because they can be used by everyone – in medieval England, villages had an open common field for grazing cattle or other livestock. No one could be excluded from using it. That also holds for the high seas: they are not under the control or jurisdiction of any one state, company, or individual person. Again in theory, no one can stop you from sailing your yacht across the Atlantic (“right of free passage”), or from fishing whatever you want in the Indian Ocean. If someone still tried to do that, there is a chance you may have encountered pirates – in which case, oh-uh, good luck?
Now I keep writing “in theory” here, because I’m an academic there are exceptions. Many of them, in fact - just as most other areas of international law, the law of the seas is wrought with overlapping norms, rules, and jurisdictions, with caveats and special cases, and spanning centuries of legal thought and state practice. For the sake of brevity, though, let’s focus on two big ones.
The first one has to do with law. For a considerable amount of time, people were generally happy with just saying the seas belong to everyone, and the coasts belong to whatever state is closest, and the rest we’ll just make up as we go. At some point, namely in the 1950s, the United Nations decided maybe someone should write down all these rules that rulers and diplomats and sailors sort of knew about before, but hadn’t actually bothered to codify. The United Nations put together a commission of lawyers to write down a Convention of the Law of the Seas (UNCLOS). Even though everyone supposedly already agreed on most things and the rules existed anyways (or so people thought), it took them 30 years to arrive at the newest version (from 1982), and then that version only became official in 1994. What does UNCLOS say? It says that the high seas are a common good and the coastline belongs to whatever state is placed there – so far so good. But then it makes some additional clarifications which actually aren’t very clear at all.
Number one, states own not only the land up to the coastline, but can also claim all territory up to 12 nautical miles from the coast into the water (“seaward”). As a coastline is usually fluctuating a bit with the ebb and flow of the seas, as well as because of erosion or other man-made or natural influences, these 12 miles are measured from a baseline defined by the mean low water mark. They are considered an extension of the state’s territory into the water, and are therefore also called “territorial waters”. That doesn’t mean that the respective state can do whatever it wants there (e.g. kill all sharks because they threaten tourists – as per other treaties, sharks are still protected animals; which coincidentally also means you may not actually just fish whatever you want in the Indian Ocean).
Number two, beyond these 12 miles of territorial waters there is a second zone of another 12 miles (so we’re at 24 from the coastline in total). That second zone is called the “contiguous zone”. This contiguous zone doesn’t technically belong to a state, but the state can still enforce some of its laws – for example on pollution. In other regards, and in contrast to the first zone which is called “territorial waters”, this zone is already part of “international waters”. So, for example, were you to sail your yacht through it, the state would have to allow you to do that (unless you tried to dump a lot of garbage into the sea, in which case…pollution laws apply). Complicated? Well, on top of that, only some states claim this zone, others don’t. It’s a bit confusing, really.
Number three, there is the 200-mile exclusive economic zone (again measured from the mean low water mark baseline). Within this zone, states have (as the name gives away) exclusive economic rights. Imagine you found oil 150 miles off the coastline. It means you can’t just try and exploit that resource all for yourself because “the seas belong to everybody”. It means that the state off of whose coast that oil was found controls it. If your oil company wants to drill, you have to get permission from that state first (and that’s likely going to be costly).

Now to be fair, even if the oil field you found laid outside exclusive economic areas (so somewhere 200+ miles away from the coast) you’d have to get permission first. In that case from the International Seabed Authority, which was set up by UNCLOS and regulates (amongst other things) the exploitation of seabed resources. Then there are international straits. And continental shelfs. And then there are the states that don’t actually have a coastline (they are “landlocked”) – is it unfair if they don’t get access to the seas? And then a lot of exceptions, special provisions, and complicated cases. What to do when zones overlap? Does the exclusive economic zone only relate to the seabed below it, or to the water and whatever is in it? Even though UNCLOS supposedly just put in writing what everyone was already doing, turns out that people did not actually agree on very many things. And even the stuff that they did agree on did not solve every problem when it came to answering who owned the seas.
Remember how I promised two big exceptions to the “global commons” idea? Number 2 doesn’t have to do with law (phew). It has to do with what states and other actors actually do. Unfortunately, but perhaps unsurprisingly (I mean, that legal stuff is difficult, right?), what the law says you can and should do is sometimes different from what you then actually end up doing. It’s no different on the seas. If you don’t do what you’re told by law, someone might call the police. If a state doesn’t do what it’s told, what happens? That depends a bit on who the wrongdoer is. Turns out that, generally speaking, the more powerful you are, the less likely you are being told by others what you can or cannot do. That also holds for things that happen on the seas. Some states choose to hunt for whales. Others ignore contiguous or exclusive economic zones. Again others draw their own maps of coastlines, continental shelfs, and territorial claims over islands and so forth, and treat those as fact.

The seas are not only an arena of power games between states, though. They are also a source of power. Throughout the ages, maritime empires controlled the seas, or at least different parts of different seas, to great effect. In ages where streets didn’t have five lanes in each direction and railways or airplanes weren’t even imagined, traveling, trading, exploring and imperial expansion happened by boat, galley, junk, and frigate, by rowing or sailing. Even today in an age of globalized trade (not least by gigantic container ships), effective control (much more so than legal ownership) of the global common of the sea is a source of great influence and power. It allows countries that have the biggest ships (today that would be aircraft carriers) and appropriate maritime strategies to project their power far away from their own shores. These ideas and concepts have fascinated authors on maritime strategy for a long time: all the way from Alfred Thayer Mahan (“The Influence of Sea Power upon History, 1660–1783”, published in 1890) and Julian S. Corbett (“Some Principles of Maritime Strategy”, 1918), to newer takes, such as George Modelski and William Thompson, “Seapower in Global Politics 1494–1993” (1988), Sam J. Tangredi, ed., “Globalization and Maritime Power” (2004), or Milan Vego, “Maritime Strategy and Sea Control: Theory and Practice” (2016).
Such a focus on influence and power, however, obscures a problem with the seas as a global common. That is: if for the most part the seas belong to everyone, and they are also an arena as well as a source of power games between states – how do we get together and fix problems that relate to oceans and the seas that no one owns but everyone wishes to control and exploit? Who is responsible for garbage clogging up the Pacific, for protecting animals, for fighting piracy (yes, that’s still a problem, here is the paper and the research article) ? Everyone – or no one? The question of how to manage the global commons is one of the biggest problems concerning the seas, and only ever more important in an age of climate change.
Author: G. M. Meibauer
Illustrator: A. Loth