33 CFR § 2.22 - Territorial sea.
(a) With respect to the United States, the following apply—
(1) Territorial sea means the waters, 12 nautical miles wide, adjacent to the coast of the United States and seaward of the territorial sea baseline, for—
(i) Statutes included within subtitle II, subtitle VI, and subtitle VII, title 46, U.S.C.; the Act of June 15, 1917, as amended (46 U.S.C. 70051–70054); and the Vessel Bridge-to-Bridge Radiotelephone Act (33 U.S.C. 1201–1208), and any regulations issued under the authority of these statutes.
(ii) Purposes of criminal jurisdiction pursuant to Title 18, United States Code.
(iii) The special maritime and territorial jurisdiction as defined in 18 U.S.C. 7.
(iv) Interpreting international law.
(v) Any other treaty, statute, or regulation, or amendment thereto, interpreted by the Coast Guard as incorporating the definition of territorial sea as being 12 nautical miles wide, adjacent to the coast of the United States and seaward of the territorial sea baseline.
(2) Unless otherwise specified in paragraph (a)(1) of this section, territorial sea means the waters, 3 nautical miles wide, adjacent to the coast of the United States and seaward of the territorial sea baseline.
(3) In cases where regulations are promulgated under the authority of statutes covered by both paragraphs (a)(1) and (a)(2) of this section, the Coast Guard may use the definition of territorial sea in paragraph (a)(1) of this section.
(b) With respect to any other nation, territorial sea means the waters adjacent to its coast that have a width and baseline recognized by the United States.