Archipelagic sea lanes passage

Archipelagic sea lanes passage (ASLP) is codified in Part IV, Articles 52–54 of the United Nations Convention on the Law of the Sea (UNCLOS, 1982). An archipelagic state, defined under Article 46 as a state constituted wholly by one or more archipelagos, may draw straight archipelagic baselines under Article 47 enclosing archipelagic waters over which it exercises sovereignty (Article 49). To balance this enclosure against navigational freedoms, Article 53 grants foreign ships and aircraft the right of archipelagic sea lanes passage through sea lanes and air routes designated by the archipelagic state for continuous and expeditious passage between one part of the high seas or an EEZ and another. The regime mirrors transit passage through straits used for international navigation (Article 38) and is non-suspendable, distinguishing it from the right of innocent passage that otherwise applies in archipelagic waters under Article 52.

Operationally, the archipelagic state may designate sea lanes and air routes "suitable for the continuous and expeditious passage of foreign ships and aircraft," including all normal passage routes used for international navigation, defined by a series of continuous axis lines (Article 53(5)). Ships and aircraft must not deviate more than 25 nautical miles from these axis lines and may not navigate closer to coasts than 10 percent of the distance between bordering islands. Proposals for designation must be referred to the competent international organization — the International Maritime Organization (IMO) — for adoption before the state may designate or substitute them (Article 53(9)). Crucially, Article 53(12) provides that if an archipelagic state does not designate sea lanes, the right may be exercised through the routes normally used for international navigation. Passage permits normal mode transit — submarines may pass submerged and aircraft may overfly — unlike innocent passage.

The leading real-world instance is Indonesia, the world's largest archipelagic state, which in 1996 submitted partial sea lanes to the IMO; the IMO's Maritime Safety Committee adopted three north–south axis lines in 1998 (effective in part from 2002), while the Lombok and Sunda strait corridors remain the principal designated lanes. The Philippines, another archipelagic claimant, has legislated baselines (Republic Act 9522, 2009) but has not formally designated IMO-approved sea lanes, leaving Article 53(12) routes operative. As of 2026 these remain flashpoints, with major maritime powers, notably the United States through its Freedom of Navigation operations, asserting that designation cannot diminish the high-seas-like character of passage.

For the exam, ASLP is tested in the international law / law of the sea segment of the General Studies and optional papers (UPSC Law optional, FSOT, CSS International Law). Typical question angles require distinguishing ASLP from innocent passage and transit passage, identifying the controlling UNCLOS articles, and explaining the IMO's gatekeeping role in lane designation. Candidates should be ready to contrast archipelagic states (Article 46) with coastal states having offshore archipelagos, and to cite Indonesia's 1998 IMO designation as the canonical precedent.