Torres Strait Treaty Decouples Seabed and Water Rights to Allow Visa-Free Border Crossing

When the United States and Canada codified Indigenous border crossings under the Jay Treaty, they applied a single rule to a single line on a map. When Australia and Papua New Guinea drew their maritime border through the Torres Strait, they did something far more complex. They separated the ocean floor from the water above it.

The 1978 Torres Strait Treaty, which officially took effect in 1985, governs the 150-kilometer stretch of water between the tip of Queensland and the coast of Papua New Guinea. It remains one of the most unusual boundary agreements in international law.

Instead of a standard vertical border extending from the seabed to the sky, the treaty establishes a bifurcated boundary. One line dictates who owns the oil, gas, and minerals beneath the sand. A different line dictates who controls the swimming fish.

Overlaid across both of these jurisdictional limits is the Torres Strait Protected Zone. This designated area suspends standard immigration laws, allowing traditional inhabitants from both nations to cross the international border without passports or visas.[1]

The arrangement solves a geographic anomaly. Fifteen Australian islands lie just off the Papua New Guinea coast, north of the primary seabed boundary. The treaty ensures that the Indigenous populations of these islands are not cut off from their traditional hunting grounds or their Melanesian neighbors.

Decoupling the Ocean Floor

Under the standard framework of the United Nations Convention on the Law of the Sea, a nation's Exclusive Economic Zone grants unified control. The coastal state manages both the seabed resources and the water column above it out to 200 nautical miles.

The Torres Strait Treaty abandons this unified approach. It establishes a Seabed Jurisdiction Line that runs roughly through the center of the strait. South of this line, Australia controls all resources on or below the ocean floor. North of it, Papua New Guinea holds sovereign rights.

However, the Fisheries Jurisdiction Line diverges from the seabed boundary. In the central and eastern sections of the strait, the fisheries line swings significantly further north, running much closer to the Papua New Guinea coastline.

This divergence means there are areas where Papua New Guinea owns the seabed, but Australia controls the commercial fishing rights in the water column directly above it. The two nations agreed to share the commercial catch quotas within these overlapping zones to prevent resource disputes.

The separation was a deliberate compromise during the intense negotiations of the 1970s. It allowed Australia to retain control over lucrative commercial fisheries and protect the livelihoods of Torres Strait Islanders, while granting Papua New Guinea the seabed sovereignty it demanded as a newly independent nation.

The Protected Zone and Free Movement

The jurisdictional lines govern commercial extraction, but the treaty’s primary objective is cultural preservation. Article 10 of the treaty establishes the Torres Strait Protected Zone, a vast area encompassing the central strait and the overlapping boundaries.[2]

Within this zone, standard international border controls do not apply to the region's Indigenous populations. The treaty permits free movement and the performance of lawful traditional activities for recognized traditional inhabitants of the area.[2]

This visa-free transit is restricted to specific communities. The agreement recognizes 14 Australian Torres Strait Islander communities and 13 specific coastal villages in Papua New Guinea whose residents hold traditional movement privileges.

Traditional activities include subsistence fishing, hunting for turtle and dugong, barter, and attending religious or social gatherings. The treaty explicitly excludes commercial enterprise; a Papua New Guinean citizen cannot use the provision to seek paid employment in Australia.

The volume of cross-border traffic is substantial. In the 2017 to 2018 period, traditional inhabitants from Papua New Guinea made approximately 27,300 visits to the Protected Zone under the treaty's provisions, according to the Australian National Audit Office.

By contrast, Australian traditional inhabitants made only about 1,000 visits to the Papua New Guinea treaty villages during the same period. The asymmetry reflects the economic and healthcare disparities between the two nations, driving more northbound traffic toward Australian islands for trade and family visits.

Australian Enclaves in Foreign Waters

The most complex geographic feature of the Torres Strait is the location of Australia's northernmost inhabited islands. Saibai, Boigu, and Dauan sit just a few kilometers from the Papua New Guinea mainland, well north of the Seabed Jurisdiction Line.

If a standard maritime boundary had been drawn, these islands would have been isolated inside Papua New Guinean waters. Instead, the treaty recognizes 15 cays, islands, and rocks north of the seabed line as sovereign Australian territory.

To prevent these islands from claiming massive maritime zones that would block Papua New Guinea's access to the sea, the treaty limits their territorial waters. Each Australian island north of the boundary is granted a territorial sea of exactly three nautical miles.

This creates a series of Australian sovereign enclaves surrounded by Papua New Guinean seabed. The Protected Zone ensures that the residents of these islands can navigate the surrounding waters and interact with nearby Papuan villages without passing through customs.

It is the only boundary treaty so far in which Australia has had to negotiate a territorial sea boundary with another country because of its proximity, a Department of Foreign Affairs and Trade official noted during a 2009 parliamentary inquiry.[2]

Managing a Porous Border

While the border is open for traditional inhabitants, it remains heavily regulated for biosecurity and customs. The Australian Border Force and the Department of Agriculture and Water Resources maintain a constant presence in the strait to monitor the movements.

The primary concern is the southward transmission of pests and diseases, such as fruit flies or exotic mosquito-borne viruses. The movement of live animals, untreated animal products, and soil from the Protected Zone to mainland Australia is strictly prohibited without a specific biosecurity permit.

Traditional vessels traveling from Papua New Guinea into the Protected Zone are exempt from standard pre-arrival reporting. However, Australian biosecurity officers still inspect these vessels upon arrival at inhabited islands to ensure compliance with quarantine regulations.

The dual nature of the border creates unique law enforcement challenges. Police and border officials must constantly distinguish between a legal traditional visitor from a treaty village and an illegal migrant from elsewhere in Papua New Guinea.

To manage this, both nations employ local liaison officers based on Thursday Island in Australia and Daru in Papua New Guinea. These officers consult regularly with village leaders to verify identities and resolve disputes over traditional fishing rights.

Protecting Vulnerable Marine Species

The Protected Zone also serves as a massive environmental conservation area. The treaty mandates that both nations take legislative measures to protect the marine environment and indigenous flora and fauna within the strait.[3]

This includes the management of vulnerable species like marine turtles and dugongs. Both species are listed under the Convention on International Trade in Endangered Species, but the treaty allows traditional inhabitants to hunt them for subsistence.[3]

The exemption for traditional hunting relies on local management plans to prevent over-harvesting. The Torres Strait Regional Authority stipulates that meat from turtles and dugongs hunted in the Protected Zone cannot be sold commercially.[3]

However, differing regulations outside the zone complicate conservation efforts. Papua New Guinean fishers retain artisanal rights to hunt turtle and dugong in their own territorial waters outside the Protected Zone, where the meat can legally be sold or bartered in local markets.[3]

The treaty requires continuous bilateral cooperation to balance these traditional rights with the survival of the species. The Torres Strait Protected Zone Joint Authority, comprising Australian federal and state ministers, formulates policies to manage the shared fisheries sustainably.

A Durable Legal Framework

The Torres Strait Treaty represents a rare instance where international law bent to accommodate local reality, rather than forcing local populations to conform to a line on a map.

By decoupling the seabed from the water column, the agreement solved a seemingly intractable sovereignty dispute. By establishing the Protected Zone, it preserved a continuous cultural and economic exchange that predates the existence of both nations.

The framework requires intense, ongoing management to function. It relies on the daily cooperation of border forces, biosecurity officers, and local village leaders to maintain the distinction between traditional movement and international smuggling.

The true test of the treaty is not its legal elegance, but its durability on the water. Four decades after its ratification, the bifurcated boundary continues to hold, allowing tens of thousands of traditional crossings each year without compromising the sovereignty of either state.