The Volokh Conspiracy Blog has an excellent post entitled, "Taiwan's Right to Representation in the UN". Amongst numerous historical arguments, the post elucidates several reasons why Taiwan deserves its own representation in the UN. The basic argument is not that Taiwan should represent China in the UN but simply that Taiwan deserves it's own seat as an independent, sovereign nation. In 1971, Twenty-two years after Chiang Kai-shek and his armies fled mainland China to Taiwan, the UN determined that Beijing and not Taipei should represent China at the UN. However, UN Resolution 2758 only addressed the question of whether the Mao or the Chiang regime should hold the seat and it was silent about the matter of Taiwan's independence.
The post stated that "it is important for the public and the diplomatic community to recognize the illegitimacy of Taiwan being denied its rightful place in the United Nations." Article 4 of the UN Charter says that "Membership in the United Nations is open to all other [non-founding] peace-loving states which accept the obligations contained in the present Charter and, in the judgment of the Organization, are able and willing to carry out these obligations." As the Volokh Conspiracy Blog pointed out:
Taiwan is indisputably a "peace-loving" state — in marked contrast to China, which not only makes threats against Taiwan, but supplies arms and financial support to warlords, dictators, and genocidaires around the world, including in Sudan.
According to China Confidential, Taiwan's application for membership in the UN has been consecutively denied 14 times. Taiwan's president, Chen Shui-bian, has promised to reapply for admission despite threats from Beijing. "Beijing is certain to cite such a move as a provocation; China's recently adopted 'Anti-Secession Law' authorizes use of force against Taiwan, a de facto sovereign state actually recognized by 24 UN member-nations, if it moves to formally declare independence or if peaceful reunification efforts fail."
The Volokh Conspiracy Blog points out that Taiwan fulfills the four criteria for de facto statehood under Article 1 of the 1933 Montevideo Convention: "(a) a permanent population; (b) a defined territory; (c) government; and (d) capacity to enter into relations with the other states." Taiwan is self-governing and a successful democratic state with a population of more than 23 million people, which is larger than most UN member states. Taiwan has a well-defined territory and Taiwan's government is sovereign over its entire territory. The post added, "Fifty-seven years of actual independence is more than sufficient for Taiwan to deserve recognition as an independent state."
One of China's main arguments for unification with Taiwan is that the island was previously under the rule of China, or at least that's the inchoate argument that is so easily used as a justification. According to the Volokh Conspiracy Blog, if this is a sound argument, then Japan has more of a claim to Taiwan than China. In comparison to the long history of China and other countries in Asia, "Only for 17 years (some other historians say 8 years) in the late 19th century did China actually declare sovereignty over all of Taiwan. This is trivially short period in the scope of Taiwanese and Chinese history." In 1895, China renounced any claim to Taiwan and it was formally ceded to Japan, which ruled the island until the end of World War II in 1945. "Today, we would hardly claim that Japan's historical record of sovereignty over Taiwan entitles Japan to rule Taiwan against its will; a fortiori, the weaker record of Chinese sovereignty cannot give China a right to rule Taiwan against its will."
Lastly, we enthusiastically concur with the Volokh Conspiracy Blog's main contention:
The fact that China persists in a claim of sovereignty of Taiwan, and sometimes makes military threats, cannot be considered a proper reason for denying UN membership to Taiwan...Rather than kowtowing to the Chinese dictatorship, all freedom-loving nations and peoples should stand in support of Taiwan's right to self-determination and to membership in the United Nations.