There is increasing talk of U.S. military options against China in military, economic, academic, and government venues. This discussion follows chiefly from China’s incrementalist military tactics of territorial acquisition in places like the South China Sea, East China Sea, and the Arunachal Pradesh region of India. It also stems from China’s support of North Korea, which increasingly threatens the U.S., South Korea, and Japan with provocative statements and nuclear weapons development. China’s actions and allies threaten international stability and the rule of international law. Because China is increasingly powerful and takes an explicit position against values like democracy and universal human rights , China threatens foundational enlightenment principles, including as instituted in European and American forms of government.

This aerial photo taken through a glass window of a military plane on May 11, 2015 shows China’s alleged on-going reclamation of Mischief Reef in the Spratly Islands in the South China Sea. China’s campaign of island building in the South China Sea might soon quadruple the number of airstrips available to the People’s Liberation Army in the highly contested and strategically vital region. That is bad news for other regional contenders, especially the U.S., the Philippines and Vietnam. Ritchie B. Tongo/Pool Photo via AP, File.

Defensive military options short of war, such as naval blockades and acquisition of nuclear weapons by Japan and South Korea, entail risk of uncontrollable escalation into military confrontation. So, states considering these risky steps should consider whether such risk of war is justified.

Just war theory finds that states have a responsibility to protect the territory of their citizens, uphold international law, and defend justice. Wars should have a just cause, be the last resort, have right intentions, possess a reasonable chance of success, and have a means proportional to the end.

 Image may contain: airplane, sky and outdoor
Chinese J-11 fighter jet. Satellite photography indicates that China has already militarised the islands it developed in the South China Sea

Consider one example — China’s continued occupation of Mischief Reef, which is in the Philippine exclusive economic zone (EEZ) as recognized by the United Nations Convention on the Law of the Sea (UNCLOS). The Philippines has an obligation to defend the territory of its citizens, such as maritime territory , so should do that to the best of its ability, including by requesting assistance from the U.S., its treaty ally. This satisfies just war theory’s recognition of the responsibility of the state to protect its citizens and territory.

Defense of an ally upholds international law, defends justice, and has right intentions. The Philippines is a U.S. treaty ally per the Mutual Defense Treaty of 1951. China occupied Mischief Reef in the Spratly Islands in 1995. In compliance with the UNCLOS dispute resolution process, the Philippines brought China to the Permanent Court of Arbitration in the Hague in 2013. This satisfies the last resort requirement of just war theory, as well as the requirement of the Mutual Defense Treaty (Article 1) that,

The Parties undertake, as set forth in the Charter of the United Nations, to settle any international disputes in which they may be involved by peaceful means in such a manner that international peace and security and justice are not endangered and to refrain in their international relations from the threat or use of force in any manner inconsistent with the purposes of the United Nations.”

Contrary to what many commentators said in the press, China can not reasonably claim the U.S.-Philippine blockade, quarantine, or other denial of access of Mischief Reef as an act of war, tantamount to war, or a casus belli (cause for war). Rather, China violated the dignity and sovereignty of the Philippine state when it occupied the reef in 1995 , and a blockade would be a reasonable attempt at enforcing international law. The Hague’s Permanent Court of Arbitration confirmed Philippine sovereignty over the feature in the 2016 findings when it states:

Having found that Mischief Reef, Second Thomas Shoal and Reed Bank are submerged at high tide, form part of the exclusive economic zone and continental shelf of the Philippines, and are not overlapped by any possible entitlement of China, the Tribunal concluded that the Convention is clear in allocating sovereign rights to the Philippines with respect to sea areas in its exclusive economic zone.”

China refused to recognize or abide by the 2016 international court ruling that its Mischief Reef occupation violated Philippine sovereignty. Following a pattern that stretches back to at least the earliest days of the Chinese Communist state, China is the first and only aggressor here. China’s continued occupation of the Philippines’ Mischief Reef is therefore just cause for a blockade of that feature , at a minimum, and at a maximum, is a casus belli. The Philippine state, having exhausted all means through the courts, now has a duty to its citizens to pursue other means, including activation of the 1951 U.S. Mutual Defense Treaty.

A U.S.-Philippine blockade would be a minimum means through which to satisfy state responsibilities to defend territories and uphold alliance commitments. To argue that such a blockade would be an “act of war” by the U.S. and Philippines and therefore unjustifiable makes no normative sense given China’s aggressor status. Economic sanctions against China would be another minimum means, should be pursued simultaneously, and would be justified by a similar line of argumentation.

War is by no means inevitable. That a U.S. blockade would cause armed clashes is a very small probability. Given armed clashes, the probability of a significant escalation, much less a broader war, is smaller still. The probability that a blockade escalates to a major war is therefore minuscule. China has had near-continuous modern border disputes, with just a few becoming violent. Militarized border disputes with Russia (1969) and Vietnam (1979), for example, did not escalate into nuclear war, despite China and Russia being nuclear powers, and an alliance between Russia and Vietnam.

Image may contain: sky and outdoor

Part of a Chinese HQ-9 Air Defense System