Under modern international law, a sovereign nation is an existence which makes areas under the control, such as territories and territorial sea clear and rule the area monistically, so an ambiguous existence such as Ryukyu, which belonged to both China and Japan was not approved.
主権国家とは、その主権が及ぶ範囲、つまり領土や領海を明確化し、そこに一元的な統治を施す存在であるから、華夷秩序下ではありえた中国・日本双方に両属する琉球のような曖昧な存在は認められなかった。