Charles Ellms 
The Story of Pirates [EPUB ebook] 

By the universal law of nations, robbery or forcible depredation upon the ‘high seas, ‘ animo furandi, is piracy. The meaning of the phrase ‘high seas, ‘ embraces not only the waters of the ocean, which are out of sight of land, but the waters on the sea coast below low water mark, whether within the territorial boundaries of a foreign nation, or of a domestic state. Blackstone says that the main sea or high sea begins at low water mark. But between the high water mark and low water mark, where the tide ebbs and flows, the common law and the Admiralty have divisum imperium, an alternate jurisdiction, one upon the water when it is full sea; the other upon the land when it is ebb. He doubtless here refers to the waters of the ocean on the sea coast, and not in creeks and inlets. Lord Hale says that the sea is either that which lies within the body of a country or without. That which lies without the body of a country is called the main sea or ocean. So far then as regards the states of the American union, ‘high seas, ‘ may be taken to mean that part of the ocean which washes the sea coast, and is without the body of any country, according to the common law; and so far as regards foreign nations, any waters on their sea coasts, below low water mark…