Indeed, according to established international law, no country should fly balloon or any other flying object in the territorial airspace of another country without the latter's consent. To put it in another way, if a country (country A) flies a balloon or some other flying object in the territorial airspace of another country (country B), it shall be regarded as a violation of international law and the territorial sovereignty of the latter. In such a case, the first country will be held liable under international law.

But there are a few pre-conditions for the above conclusion to be held true. The first is that country A has not obtained prior consent from country B for flying the balloon in its territorial airspace. The second condition is that the balloon or any other flying object is fully controlled by country A when it enters the airspace of country B.

If country A, having full control of the balloon, deliberately directs the balloon into the territorial airspace of country B, country A can be held liable. But if the balloon, in full control of country A, drifts into the territorial airspace of country B, no country should be held liable.

The third condition is that the balloon flies into the territorial airspace of country B.

Were the three preconditions met in the case of China's balloon (civilian airship) which the United States shot down on Feb 4? Perhaps not.

China has made clear the balloon was mainly used for meteorological purposes (to collect meteorological data) — not intended to spy on the US or any other country.

And no, China could not have obtained the US' consent before flying the balloon in that country's airspace, simply because the balloon went out of control due to force majeure and after an uncharted months-long journey, unexpectedly drifted into the space above the US. China did not know the drifting course of the balloon when it went out of control, and it was impossible for China to predict where the balloon would fly to.

According to a general rule of the law of logic, if one of the above preconditions is not met, the aforementioned conclusion cannot sustain. Therefore, although the Chinese balloon drifted into the airspace over the US, China cannot be held accountable for that, because the balloon had gone out of control much before that. China had no intention of flying that balloon into the airspace over the US territory.

According to an old dictum, no one should be liable for an act that is not attributable to him. Similarly, no liability should be attributed to China in this case, because it is not accountable for it.

In conclusion, China cannot be held liable under international law for the balloon that drifted into the airspace over the US. And the US should not have shot down the balloon as long as it had no evidence to prove the balloon posed a threat to the country's people and/or property. Despite calling it a "spy balloon", Washington has no evidence to prove it was indeed a "spy balloon".

As a matter of fact, after the balloon was seen in the airspace over the US, its official said it does not pose any military or physical threat to the people on the ground. Yet the US shot down the balloon, revealing, once again, its hostility toward China. The US surely knows that, in general, countries around the world have not destroyed or shot down any foreign flying object that accidentally entered their country's airspace.

This shows China was not at fault according to international law, and the US action was against the general national practice.

Since the US has destroyed Chinese property, it should at least hand over its remains to the owner. It should also refrain from taking any more action concerning the remains of the balloon to mitigate the loss of Chinese.

The author is the dean of the School of International Law, China University of Political Science and Law. The views don't necessarily reflect those of China Daily.

The views don't necessarily reflect those of China Daily.