Taiwan's sovereignty is a sensitive issue in Taiwan. Unfortunately, there is a lot of misinterpretation of the several important international legal documents and treaties regarding this issue.
I would like to address the misinterpretations that the Treaty of Shimonoseki and the Potsdam/Cairo declarations were not valid because they didn't meet the conditions set by international laws on the conclusion of treaties.
Japan renounced any rights and claims to Taiwan and the Pescadores according to Article 2b of the 1952 Peace Treaty of San Francisco.
Some people suggest that according to Article 10 of the subsequent Treaty of Taipei, concluded between the Republic of China (ROC) and Japan, Taiwan and the Pescadores were returned to the ROC. This view is wrong. Since Japan already renounced Taiwan and the Pescadores, logically Japan cannot transfer Taiwan and the Pescadores again to any state, simply because Japan was not the owner of these territories anymore. The treaty was abrogated by Japan at the request of the People's Republic of China (PRC) government, when the two states established diplomatic relations.
The Chinese nationalists overthrew the Qing imperial government in 1911 and established a new republican government called the Republic of China. The international community then recognized the new government as the sole legitimate Chinese government.
The same thing happened in 1949. The Chinese communists overthrew the ROC government and established the PRC government. The newly established government requested the UN expel the ROC representatives from the UN, on the grounds that the PRC succeeded the ROC, and according to international law that the succeeding government inherits all rights and obligations from the preceding government.
The current status of Taiwan is an occupied area under the effective control of the illegitimate Chinese government. According to international law regarding the succession of governments, there can be only one legitimate government per state, and the only legitimate Chinese government currently is the PRC government, therefore Taiwan belongs to China. In other words, the ROC is the reason that Taiwan belongs to China.
In conclusion, the only way Taiwan can achieve indepen-dence is to declare itself independent and to seek UN membership and recognition by other states.