The rule by which a state has territorial sovereignty of that coastal sea within three miles of land. Its name derives from the fact that in the 17th century this limit roughly corresponded to the outer range of coastal artillery weapons and therefore reflected the principle terrae dominum finitur, ubi finitur armorium vis (the dominion of the land ends where the range of weapons ends). The rule is now not widely recognized: many nations have established a 6- or 12-mile coastal limit. See also territorial waters.
From: cannon-shot rule in A Dictionary of Law »