A Chinese security expert, however, has cast doubt on Tokyo's unofficial view that the MSDF destroyer might have entered the Chinese waters by mistake, citing the Japanese crew's skill levels. The UN Convention on the Law of the Sea recognises the right to "innocent passage," allowing for a vessel to pass through the territorial waters of another state unless it compromises the safety of the coastal state. [...] Tokyo maintains that Suzutsuki's entry into Chinese territorial waters was not illegal, citing the right to innocent passage. But Beijing argues the MSDF ship did not fulfil its requirements under Chinese domestic law that foreign vessels seek its prior permission to enter its waters, the Chinese sources said. Jun Tsuruta, an associate professor of international law at Meiji Gakuin University in Tokyo, said there has been a debate about whether the right to innocent passage can be granted to military vessels as well as commercial ships and that the issue has not been completely settled based on UNCLOS adopted in 1982.