According to Kaisen Shikimoku (the oldest sea law of Japan), common law of Kaizoku-shu (pirates) drafted on the pretense of statutory law of Kamakura Bakufu Government in the Mromachi Period, confiscation of a wrecked ship was allowed only when no survivor nor owner of the ship was found but otherwise prohibited without consensus of survivors or shipowners, if any.
室町時代に海賊衆の慣習法が鎌倉幕府制定法に仮託されて法としてまとめられたとされる廻船式目によれば、寄船に生存者がいた場合や船主が明らかな場合には無断の押収を禁じ、無主物のみを認めている。