International Court of Justice

In 1949, the International Court of Justice made a historic ruling in the Corfu Channel case involving the legal definition of an international strait. The Court ruled and the 1958 Geneva Convention on the Territorial Sea and the Contiguous Zone further codified that geographically, an international strait is any strait that connects two portions of the high seas. However, the court also ruled that an international strait must fulfill a functional definition of being a useful, not just potentially useful, route for international maritime traffic. This geographic and functional definition was later reiterated by the 1982 United Nations Convention on the Law of the Sea. The definition is in keeping with the freedom of the high seas doctrine and substantially reduces the legal capacity of any coastal state to hinder the freedom of movement of seagoing vessels between the oceans of the world.

On the subject of international straits, there is debate in the Arctic about whether or not the Northwest Passage north of Canada is an international strait. The United States holds that the Northwest Passage is indeed an international strait and has repeatedly asserted this view. Indeed, the repeated northern passages of United States submarines without Canadian permission as well as the Manhattan and Polar Sea incidents are all practical demonstrations of the United States' unwillingness to concede that the straits of the Northwest Passage constitute part of international waters.

If a significant number of vessels make the voyage through the Northwest Passage or another northern passage, such as the Northern Sea Route, without first consulting the neighboring state then that state risks losing control of the passage. A nation's legal jurisdiction is significantly limited within an international strait, as the International Maritime Organization's guidelines rather than domestic regimes apply to the governance of environmental and shipping practices within international straits. This could impose significant environmental costs near environmental state.

A state bordering an international strait is allowed to maintain “sovereignty or jurisdiction over such waters and their air space, bed and subsoil”—Canada would not lose the right to explore and exploit the mineral resources of the Northwest Passage if it were classified as an international strait. However, Canada does risk losing much of the control it currently claims but often does not exercise over traffic through the Northwest Passage. Indeed, a ruling that the Northwest Passage constitutes an international strait would grant the right of transit passage beyond innocent passage to vessels and aircraft using the Northwest Passage. One matter of concern this presents is that under Article 42 of UNCLOS, should a vessel or aircraft engaged in transit passage act in a manner contrary to accepted international laws and regulations, the flag state of a ship or state of registry of an aircraft bears international responsibility for resulting loss or damage to states bordering straits.  This is important because more than half of the world's operating ships are registered under a flag of convenience in order to reduce operating costs or avoid government regulations.  States frequently used as a flag of convenience may be unwilling or unable to pay damages resulting from the operations of vessels flying a flag of convenience. As such, states bordering Arctic international straits might bear a disproportionate share of the risk associated with increased use of Arctic straits. These risk costs would be incurred beyond the additional costs associated with the optional but almost certainly necessary installation and maintenance of navigational markers denoting sea lanes through an international passage by bordering states as provided for under Article 41 of UNCLOS.

Finally, if any Arctic strait is accorded status as an international strait it would open the region to transit passage of naval vessels. During transit passage, ships are required by UNCLOS to “refrain from any threat or use of force against the sovereignty, territorial integrity or political independence of States bordering the strait” as well as to refrain from engaging in marine scientific research and hydrographic surveys without prior authorization from bordering states.  In an international strait, however, submarines are permitted to voyage in their normal subsurface mode of operation whereas in a territorial sea, subsurface vessels are required to operate on the surface and to show their flag.  Naval traffic would pose a national security threat to Arctic states bordering waterways judged to be international straits.