Passage One Questions 21 to 25 are based on the following passage. The sea is the common property of all nations. It belongs equally to all. None can appropriate it exclusively to themselves；nor is it “foreign” to any. This was the decision of John Marshall, chief justice of the United States from 1801 to 1835. It was stated as a fundamental rule the sea that no one, and therefore everyone, owns the ocean. This means that outside territorial waters(the waters within three miles of a country's coast), the law is whatever nations agree on in peacetime and whatever the strongest naval powers can enforce in wartime. After the United States purchased Alaska, Americans began to seize Canadians who were hunting seals outside Alaskan territorial waters. The Americans claimed that the seals were American property because they often came in to the Alaskan shores owned by the United States. International arbitrators disagreed with this reasoning. In some cases, however, the special rights of a nation that makes use of an open-sea area are recognized. All of the sea's rules of the road are established by international conferences and treaties. The fundamental rule of the sea means that______.