Experts warn Japan could argue it has the islands under its effective control International law experts have warned that repeated expulsions of Chinese activists by the Japanese from waters of the disputed Diaoyu islands could strengthen Tokyo's claim to the islets. Ten Hong Kong, mainland and Taiwanese activists abandoned a plan to land on the disputed islands last Thursday after their protest ship was repeatedly rammed by Japanese coastguard vessels. Thirteen Hong Kong and mainland activists made another failed attempt in June. Xinhua has released pictures of the Diaoyu activists' voyages in what is believed to be the first time state media has endorsed the protest, signalling an apparent change of official attitude. According to principles of international law, occupation, or exercise of effective control, is a method of acquiring territory that belongs to no one. Michael Davis, a professor of law in the department of government and public administration at the Chinese University of Hong Kong, said the activists' expulsion could provide evidence for Japan's actual control of the islands. 'By expelling Chinese activists from the Diaoyu islands, the Japanese government is trying to establish a case for actual and uninterrupted possession of Diaoyu islands over a long period of time,' Professor Davis said. But the professor, an expert on international conflicts, said the expulsion of Chinese activists would not be strong evidence if the case was brought to the International Court of Justice in The Hague. South Korean activists had taken similar action during their fight with Japan over the sovereignty of Tokdo, the tiny islands in the Sea of Japan in the past few decades. South Korea built wharf facilities on the islands in 1993 and a lighthouse in 1997. In July 1997, more than 500 South Koreans protested at the seizure of South Korean fishing boats in the disputed waters by Japanese coastguards. So far neither country has taken the case to the International Court of Justice. Priscilla Leung Mei-fun, associate professor with the City University's school of law, said repeated expulsions of Chinese activists could give Japan an opportunity to claim that the Diaoyu islets were under its effective control. 'But the dispute over sovereignty ... remains unresolved as long as the Chinese government reiterates its claim of sovereignty.' But Dr Leung said the activists' attempts to land could show the islets were disputed territories. Professor Davis and Dr Leung said China and Japan were unlikely to take the case to the international court.