【文/田士臣 何柳】

正如美军射击中国气球违反了联合国禁止非法使用武力的原则一样，美国如有任何对台海冲突的军事干预，都会使之成为中国领土的侵略者。

早在美国前众议院议长南希·佩洛西窜访台北之前，台湾问题就一直是美国政府官员以及国会、学术界和智库人士深入、频繁和定期辩论的话题。最新讨论的焦点是新当选的众议院议长麦卡锡可能窜访台湾，以及中国国防部为其窜访后果所做的军事准备。

但是，他们一方面热烈讨论美国不可避免地对假定的两岸冲突进行军事干预的情况，另一方面似乎从不忘记批评中国政府“和平统一但不承诺放弃使用武力”的政策，然而他们始终忘记讨论——或者说视而不见——的问题是：美国的这种干预是否存在合法性和正义性。

根据国际法，美国对两岸冲突进行军事干预的法律依据是什么？要回答这个问题，我们需要研究美国可能进行军事干预的原因。

智库与美国专家的对话显示，约80%的受访者提到了“保卫民主”。另有15%的人援引了《与台湾关系法》(Taiwan Relations Act)，尽管这只是美国的国内法。另外5%的人坦率地承认，从战略上、地缘政治上和军事上讲，美国不能“失去”台湾。

关键问题是，这三类原因在国际法上是否站得住脚。根据《联合国宪章》和国际习惯，合法使用武力的情况只有两种：一是联合国安理会授权，二是自卫权。美国的三种军事干预的理由都不属于合法使用武力的两种情况。

所谓“保护民主”和“执行国内法”都不是禁止非法使用武力原则的合法例外。否则的话，任何国家都可以通过声称保护民主或通过制定国内法自由使用武力。

似乎没有人质疑美国在两岸冲突中使用武力的合法性，然而，一个国家使用武力收回其反叛省份——就像中国大陆和台湾的情况——却被美国称为“侵略”或“入侵”行为。

虽然这两个词在英语中是不同的，但在汉语中这两个词只能被翻译成同一个词——侵略。这是一个分量很重的词，人们倾向于把它等同于英语中的“侵略”（aggression）。

美国频繁在台海周边进行军事演习（图片来源：ICphoto）

但在国际法上，“侵略”一词是有特定含义的，无论是1974年12月14日联合国大会通过的《关于侵略定义的决议》（第3314号决议），还是国际刑事法院成员国于2010年6月12日通过的《罗马规约》关于侵略罪的修正案，对侵略行为和侵略罪的认定有严格规定。

按照上述两个国际文件共同确认的规定，“侵略行为”是指一国使用武力或以违反《联合国宪章》的任何其他方式侵犯另一国的主权、领土完整或政治独立的行为。

一个中国原则已经被国际社会通过联合国决议确认，包括美国在内的世界上绝大多数与中国建立外交关系的主权国家也在双边层面对此予以认可。既然台湾不是一个国家而只是中国的一部分，中国恢复对台湾行使主权的行为，即使使用武力也是一个主权国家内部的使用武力，而非国与国之间的使用武力。

中国怎么可能会是国际法上的“侵略行为”呢？然而，如果美国进行军事干预，它将是侵略者，违反了联合国禁止在国际关系中使用武力的基本原则入侵中国领土。

默许美国可能进行非法的军事干预，同时质疑中国政府使用武力的合法权利，只会加剧对国际法中美国例外论已经猖獗的容忍。

这不仅引发了对西方道德操守的质疑，也破坏了《联合国宪章》所载的集体安全体系，该体系的宗旨是“使子孙后代免于在我们的一生中两次给人类带来无尽痛苦的战祸”。

美军击落因不可抗力进入美国领空的中国无人民用飞艇，又开了一个危险的先例，违反了《联合国宪章》关于禁止非法使用武力的基本原则。

即使美国想击落气球，它也应该动用执法机构来执行这项任务。鉴于中国外交部多次表示气球是一艘无人驾驶的中国民用飞艇，美国使用其军事执法机构而不是民事执法机构明显违反了《联合国宪章》第2(4)条。

我们希望美方注意到这一条的规定：“所有成员国在其国际关系中不得威胁或使用武力侵犯任何国家的领土完整或政治独立。”

【本文作者田士臣为经士智库创始人兼国际军事行动法研究中心主任，何柳为上海政法学院助理研究员。】

英文原文：

Long before former US House Speaker Nancy Pelosi’s high -pro?le visit to Taipei, the Taiwan issue had been deeply, frequently and regularly debated by US government ofcials, and those in Congress, academia and think tanks.

The latest discussion focuses on a possible visit by newly elected House Speaker Kevin McCarthy and the Defence Department’s military preparations for the consequences of such a visit.

But as they hotly debate the scenario of an inevitable US military intervention in a hypothetical cross -strait con?ict, they forget to discuss – or they turn a blind eye to – the legality and justness of such an intervention. Yet they never seem to forget to criticise the Chinese government for its policy of peaceful reuni?cation with Taiwan while not abandoning the right to use force.

What legal basis does the US have, under international law, to intervene militarily in a cross -strait con?ict? To answer this, we need to examine the reasons for a possible US military intervention.

Think-tank dialogues with US experts show that about 80 per cent cite the protection of democracy. Another 15 per cent cite the Taiwan Relations Act, although this is merely US domestic law. The other 5 per cent frankly admit that, strategically, geopolitically and militarily, the US cannot aford to “lose” Taiwan.

The critical issue is whether these three categories of argument hold water under international law. This, as re?ected in the UN Charter and international custom, only prescribes two scenarios for the    legitimate use of force: UN Security Council authorisation or the right of self-defence. None of the three US categories of defence falls into either of the two scenarios for the legitimate right to use force.

Neither protecting democracy nor implementing domestic law is a lawful exception to the general prohibition against the use of force. If they were, any country could freely use force by claiming to be protecting democracy or through the enactment of a domestic law.

And while no one seems to question the legality of the use of force by the US in case of a cross -strait con?ict, a motherland using force to take back its rebellious province – as would be the case for mainland China and Taiwan – is termed an act of “aggression” or an “invasion” .

Although those two words are diferent in English, there is only one word for both in Chinese – qin lue (侵略). This is a weighty word and people tend to equate it with aggression.

But the term “aggression” has a speci?c meaning in international law, whether in the resolution on the “de?nition of aggression” adopted by the UN General Assembly on December 14, 1974, or in the     amendment to the Rome Statute on the crime of aggression, adopted by the member states of the International Criminal Court on June 12, 2010. The determination of an act of aggression and the crime of aggression are strictly regulated.

In accordance with the provisions of the two international instruments, an “act of aggression” refers to the use of force by a state against the sovereignty, territorial integrity or political independence of another state or in any other manner contrary to the UN charter.

The one-China principle has been con?rmed by the international community through UN resolutions. It has also been recognised at the bilateral level by most sovereign nations, including the United States, which conducts diplomatic relations with China. Since Taiwan is not a country but part of China, even if the Chinese government uses force to restore its sovereignty over Taiwan, it would be a sovereign act rather than one between states.

How could that be taken as an act of aggression under international law? If the US were to intervene militarily, it would be the aggressor, violating the UN’s fundamental principle against the use of force in international relations, in invading Chinese territory.

Acquiescence to a potentially unlawful US military intervention while questioning the Chinese government’s legitimate right to use force only adds to the already rampant tolerance of American exceptionalism in international law.

This has not only led to questions about the moral integrity of the West, but has also destroyed the collective security system enshrined in the UN Charter, which was designed “to save succeeding generations from the scourge of war, which twice in our lifetime has brought untold sorrow to mankind” .

The US military, in shooting down an unmanned Chinese civilian airship that had ended up in US airspace due to force majeure, has set another dangerous precedent, violating the fundamental principle of the UN Charter on the prohibition of the use of force.

Even if the US wanted to neutralise the balloon, it should have employed its law enforcement agencies to carry out the mission. Given that China’s foreign ministry has repeatedly said the balloon was an unmanned Chinese civilian airship, America’s use of its military instead of civilian law enforcement agencies is a clear violation of Article 2 (4) of the UN Charter.

This states, and we hope the US takes note, that: “All members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state. ”