U.S.-China relations, never simple, are likely to be further complicated by the expected landslide election tomorrow of Tsai Ing-wen as the new president of the Republic of China on Taiwan. Tsai is the chair of the traditionally pro-independence Democratic Progressive Party and many – though not all – of her supporters want Taiwan to declare formal independence from China. Tsai has been careful not to over-commit herself on independence so as not to overly antagonize China or the U.S. – which is, in turn, worried about antagonizing China. But given her party’s pedigree, China is likely to be less friendly, if not overtly hostile, towards the new Tsai DPP government. Note, China has never ruled out the use of military force to ensure Taiwan’s unification with the country.

With that in mind, it is worth considering whether and to what extent the U.S. has an obligation – legal or otherwise – to defend Taiwan against military action by China. Commentators, such as Richard Bernstein writing in Foreign Policy, sometimes refer to a U.S. obligation “to intervene if China launched an armed strike on Taiwan.” As a legal matter, this is both not quite right and not exactly wrong. While the U.S. does not have a strict legal obligation to defend Taiwan against an attack by China, in my view, the U.S. does not have a strict legal obligation to defend its other allies either.

Here, the relevant legal document is the Taiwan Relations Act (TRA). The legislation was enacted by Congress in 1979 following the U.S. decision to cut ties with Taiwan, abrogate the U.S.-Republic of China (Taiwan) Mutual Defense Treaty, and establish relations with China. The TRA is frequently cited by U.S. policymakers as the legal framework governing Taiwan policy actions. In reality, although the TRA has practical importance for civil and commercial relations with Taiwan, it does not strictly bind U.S. policymakers with respect to US-China-Taiwan relations.

TRA Sections 2 and 3 contain the key provisions with respect to military defense of Taiwan. Section 2 declares as a matter of U.S. policy that the U.S. expects the “future of Taiwan will be determined by peaceful means,” that “any effort to determine the future of Taiwan by other than peaceful means, including by boycotts or embargoes, [is] a threat to the peace and security of the Western Pacific area”, and “to maintain the capacity of the United States to resist any resort to force or other forms of coercion that would jeopardize the security, or the social or economic system, of the people on Taiwan.”

Section 3 implements this policy by requiring that the U.S. government “make available to Taiwan such defense articles and defense services in such quantity as may be necessary to enable Taiwan to maintain a sufficient self-defense capability.” It further requires the President “to inform the Congress promptly of any threat to the security or the social or economic system of the people on Taiwan and any danger to the interests of the United States arising therefrom.” Finally, the TRA requires the “President and the Congress shall determine, in accordance with constitutional processes, appropriate action by the United States in response to any such danger.”

On its face, the TRA appears to only require the U.S. to sell defensive materials to allow Taiwan to maintain self-defense and for the President to inform Congress of any threat to the security of Taiwan. If China launched a military assault, the President is only legally obligated to “determine, in accordance with constitutional processes, appropriate action.” This requirement is for executive-legislative consultations and hardly seems like an obligation, as Bernstein alleges, “to intervene if China launched an armed strike on Taiwan.”

Therefore, Taiwan would be wise to not be overly comfortable regarding its U.S. security guarantee. Legally, it’s not much of a guarantee at all. However, the TRA should also not be dismissed as legally inconsequential with respect to U.S. obligations. After all, other U.S. defense guarantees in the region are not much more robust than the TRA.

For instance, Article V of the U.S.-Japan Security Treaty simply states that “[e]ach Party recognizes that an armed attack against either Party” in areas administered by Japan “would be dangerous to its own peace and safety.” The U.S. and Japan agree that each country “would act to meet the common danger in accordance with its constitutional provisions and processes.” The same language is found in the analogous provisions in the Korea, Philippines, and Australia-New Zealand defense treaties.

In all of these defense guarantees, the only really meaningful U.S. obligation is to “act to meet the common danger in accordance with its constitutional provisions.” This probably means that the U.S. president must respond to the common danger by acting on his own, or by going to Congress for authorization. But an armed response is not actually required. Thus, the TRA’s requirement that the President and Congress determine an “appropriate response” to threats to Taiwanese security or U.S interests is only somewhat weaker than what we see in other defense agreements in the region. In each case, the U.S. does not have a strict obligation to use armed force to defend the treaty partner.

Indeed, the Japan treaty’s language that an “armed attack” would be dangerous to U.S. “peace and security” is not much stronger that the TRA’s declaration that non-peaceful means to determine Taiwan’s future – e.g. an armed attack by China – is a “threat to peace and security.” The real difference is that the TRA characterizes an armed attack by China as a “threat to peace and security in the Western Pacific area[,]” whereas the Japan treaty states it is the U.S.’s “own peace and security” at stake. This difference is important, but it is also not as large as it might seem; the U.S. has often treated the magic words “threat to peace and security” as a sufficient basis to justify the use of military force.

The actual practical difference is probably that the Japan treaty would satisfy the right of collective self-defense in the U.N. Charter, whereas the TRA would not. But because the international legality of a U.S. defense of Taiwan is questionable at best, the more relevant question is what U.S. domestic law requires.

The bottom line is there is little difference between the U.S. defense obligation to Japan (and Korea and the Philippines) and its obligations to Taiwan. In each case, the U.S. declares certain actions to be threat to “peace and security” and promises to use its constitutional processes to formulate a response. While the guarantees to Japan, Korea, the Philippines, Australia, and New Zealand are certainly stronger than those to Taiwan, they are not stronger by much.

Ultimately, the core of any security guarantee is not legal obligation, but political will. Legally speaking, Taiwan lacks an ironclad U.S. security guarantee against an attack by China, but this is true for just about everyone else as well – including NATO. Whether the U.S. will come to the defense of Taiwan, or any other country, is largely contingent on questions of diplomacy, military facts, and political will. Hopefully, Taiwan’s new president understands this.