WordNet
n. the limit of a nation's territorial waters
Wikipedia
The three-mile Limit refers to a traditional and now largely obsolete conception of the international law of the seas which defined a country's territorial waters, for the purposes of trade regulation and exclusivity, as extending as far as the reach of cannons fired from land. (Improvements in cannons eventually allowed them to be able to fire a shell more than three miles, but Earth's curvature made this moot. From a height of a few meters above sea level (say, atop the wall of a coastal fort), the horizon is only about three miles (5 km) away. Thus there was no need to be able to shoot farther, since more distant targets would not be visible.)
In Mare clausum (1635) John Selden endeavoured to prove that the sea was in practice virtually as capable of appropriation as terrestrial territory. As conflicting claims grew out of the controversy, maritime states came to modulate their demands and base their maritime claims on the principle that it extended seawards from land. A workable formula was found by Cornelius Bynkershoek in his De dominio maris (1702), restricting maritime dominion to the actual distance within which cannon range could effectively protect it. Most maritime nations adopted this principle, which developed into a limit of three nautical miles. (It has also been suggested that the three-mile limit derived, at least in some cases, from the general application of the league (a common unit of measurement at sea) rather than from the range of cannon.)
Since the mid-20th century, numerous nations have claimed territorial waters well beyond the traditional three-mile (5 km) limit. Commonly these maritime territories extend from a coastline, and this was eventually established as the international norm by the 1982 United Nations Convention on the Law of the Sea. As a result, the three-mile limit has become largely obsolete. , only Gibraltar, Jordan, Palau, and Singapore retain it.
Usage examples of "three-mile limit".
Many favored Gorth: He was in the full flush of strength and, after all, had good reason to challenge the Tai-Pan if there was truth to the rumor that Culum was poxed and that, knowing this, the Tai-Pan had sent Tess and Culum to sea with a captain who could marry them beyond the three-mile limit.
New quick-freeze techniques allowed boats to work halfway around the world and process their fish as they went, and this made the three-mile limit around most countries completely ineffectual.
For the sake of completeness, I must also mention a third preposterous fable, according to which my grandfather floated out to sea like a piece of driftwood and was promptly fished out of the water by some fishermen from Bohnsack who, once outside the three-mile limit, handed him over to a Swedish deep-sea fisherman.
The Skipalong, believed to be a contact boat used by the Purple Shirt Mob for meeting contraband runners outside the three-mile limit.
The instant the Star of David entered the three-mile limit off Palestine she would be boarded by a British landing party and towed off to Haifa.
Zwillman had shot a rival named Leo Kaplus in the testicles rather than through the heart, and in 1938 Tony Cornero had established a gambling ship that stayed outside the three-mile limit off the coast of Santa Monica.
She came ashore in 1925 and when a rumrunner came inside the three-mile limit to save her crew the Coast Guard captured the whole kit and kaboodle of 'em.
They crossed the three-mile limit at eight o'clock, and crept close in under the Danish headlands without a glimmer of light showing.
We'll move in to the three-mile limit and the Seahawks can get you there and back with a load of twenty hostages.
The lumbering oil tankers belched out their contents at oiling buoys anchored on the three-mile limit.