from
The Collaborative International Dictionary of English v.0.48
Territorial waters \Ter`ri*to"ri*al wa"ters\ (Internat. Law)
The waters under the territorial jurisdiction of a state;
specif., the belt (often called the
{marine belt} or
{territorial sea}) of sea subject to such jurisdiction, and
subject only to the right of innocent passage by the
vessels of other states.
Perhaps it may be said without impropriety that a
state has theoretically the right to extend its
territorial waters from time to time at its will
with the increased range of guns. Whether it would
in practice be judicious to do so . . . is a widely
different matter . . . . In any case the custom of
regulating a line three miles from land as defining
the boundary of marginal territorial waters is so
far fixed that a state must be supposed to accept it
in absence of express notice. --W. E. Hall.
[Webster 1913 Suppl.]