While the U.S., like Japan, no longer formally recognizes Taiwan as a nation, it continues to sell arms to the T'aipei government to ensure that it has the capacity to defend itself. That is a legal obligation enshrined in the Taiwan Relations Act 台灣關係法『台湾関係法』, which was promulgated and passed by the U.S. Congress in the aftermath of the U.S. decision to switch recognition from T'aipei to Beijing.
The TRA, as the bill is known, has infuriated Beijing, which insists that Taiwan is a renegade province and argues that the arms sales encourage 'splittists' in Taiwan.
Moreover, the Chinese argue that the continuation of American weapons sales to Taiwan violate commitments made in the Shanghai Communique of 1982, in which the U.S. promised to decrease and ultimately end those deals. A slightly more sophisticated — but more chilling — argument is that the U.S. relationship with China is more important than its relationship with Taiwan and, therefore, the U.S. should bend to Chinese wishes for the greater good.
The U.S. counters that its commitment to Taiwan is based on legal and moral interests. The TRA obliges Washington to help Taiwan meet its defense needs. As long as T'aipei feels threatened, the U.S. is there to help.
The moral dimension is simple: Taiwan is a democracy and its future should be determined by its citizens, not the hulking giant next door. Washington also argues that relations with Taiwan are an indication of its commitment to the region more generally; if the U.S. were to turn its back on Taiwan, it would send a chilling signal to other U.S. allies and partners about U.S. credibility more generally. There can be no indication that the U.S. is prepared to sacrifice its partners to keep China happy..."
The second reason is that the sale likely strengthens the position of Taiwan President Ma Ying-jeou (Mǎ Yīngjiǔ) 馬英九, demonstrating that he, unlike his predecessor, enjoys good relations with the U.S. This should help him in the presidential campaign next year, and China would prefer to see Mr. Ma win a second term, rather than an opposition politician inclined toward independence of Taiwan.
If Beijing is so upset about the Taiwanese arms purchases, then it should do more to lessen the sense of threat that compels the Taipei government to want them.
There are more than 1,100 Chinese missiles targeting Taiwan. Despite Taiwanese complaints, Beijing continues to add to that inventory. China could easily redeploy the missiles so that they pose no threat to Taiwan. Of course, they are mobile missiles, so such a move would be temporary at best. But it would send a signal about Chinese intent and undermine the call for additional weapons in the future.
Cross-strait peace should be built on a genuine sense of peace shared by both parties; not unilateral disarmament by one side."