Because there are some very good people at the Cato Institute: Ted Galen Carpenter and Justin Logan are two of them:
Taiwan News Online: ince the Taiwan Relations Act of 1979, the United States has been legally obligated to sell Taiwan 'arms of a defensive character' in order to help deter the PRC from attempting to retake the island by force. In 2001, the Bush administration offered Taiwan an arms sale of roughly US$20 billion to counter a campaign of Chinese military modernization aimed directly at retaking Taiwan. Recently, a version of that package, scaled back to US$18.2 billion, was approved by Taiwan's cabinet, but remains held up in the Legislature.
Opponents of the arms sales package lament that the weapons are too expensive, and that the island has other priorities.... Taiwan's lack of seriousness is unacceptable because it has the effect of pushing the United States to the forefront of the cross-strait conflict.... One apparent factor in Taiwan's irresponsibility is that it is banking on a U.S. security guarantee. However, Taiwanese legislators (and more than a few U.S. officials) would do well to take another look at the Taiwan Relations Act, which some allege commits the United States to defend Taiwan's autonomy.
The act merely asserts that 'efforts to determine the future of Taiwan by other than peaceful means, including by boycotts or embargoes, would be a threat to the peace and security of the Western Pacific area and of grave concern to the United States.'... [I]t is possible that the United States could decide to involve itself in a conflict between Taiwan and China. That decision would be ill-advised in its own right, given the potential dangers, but it certainly should not be left to Taiwan's government to force such a momentous decision....
The United States should continue, under the obligation of the Taiwan Relations Act, to sell Taiwan defensive arms with which it can deter a Chinese attack. However, at the same time, Washington should indicate to Taiwan that it does not intend to involve itself in a war in the Taiwan Strait. As things stand now, the Taiwanese increasingly expect that the United States will defend them, and the Chinese increasingly suspect that it will not. That is the worst of both worlds, and portends a perilous situation for all parties involved.
I'm not sure I agree with them, however. It seems to me that it would be a very good idea for the U.S. to establish as a founding principle of twenty-first century international law that there will be no net loss of democracy: that changes in the status of Taiwan vis-a-vis China need to be approved by popular vote, and that any alternative makes it less rather than more likely that Taiwan will be a part of China in the long run. The right model seems to be the EU-accession model: China and Taiwan will negotiate changes in status when China has a polity and an economy attractive enough to make closer links seem a no-brainer.