"They [the adjacent waters] are, therefore, in the language of diplomacy and of international law, termed by a convenient metaphor the territorial waters of Great Britain, and the same or equivalent phrases are used in some of our statutes denoting that this belt of sea is under the exclusive dominion of the State. But the dominion is the dominion of Parliament, not the dominion of the common law. That extends no further than the limits of the realm. In the reign of Richard II the realm consisted of the land within the body of the counties. All beyond low‑water mark was part of the high seas. At that period the three‑mile radius had not been thought of. International law, which, upon this subject at least, has grown up since that period, cannot enlarge the area of our municipal law, nor could treaties with all the nations of the world have that effect. That can only be done by Act of Parliament. As no such Act has been passed, it follows that what was out of the realm then is out of the realm now, and what was part of the high seas then is part of the high seas now; and upon the high seas the Admiralty jurisdiction was confined to British ships. Therefore, although, as between nation and nation, these waters are British territory, as being under the exclusive dominion of Great Britain, in judicial language they are out of the realm, and any exercise of criminal jurisdiction over a foreign ship in these waters must in my judgment be authorized by an Act of Parliament." (emphasis added)