Australia may have "perfect right" to sail through the South China Sea (Australia asserts right to South China sea passage; April 21), but in causing China to challenge Australia's warships, the latter must have shown a total lack of courtesy to the former's navy which was carrying out an exercise in the South China Sea.

China had declared its drill zone in advance, so Australia cannot claim ignorance of where it is.

Indeed, China calling out Australia's misguided adventurism in the South China Sea serves to check the beliefs of white supremacy and "might makes right". As Mr Leslie Fong has noted, only China can do this (Who else but China can rein in Uncle Sam?; April 22).

If it was the Australian navy calling out the Chinese navy in the South China Sea, Australia's Defence Department would have wasted no time in detailing the supposed transgressions of the Chinese warships.

As it is, it was the Chinese navy calling out the Australian navy.

It can only be one of two possibilities.

One, the Australian warships are carrying out so-called Freedom-of-Navigation operations and were intercepted, challenged and warned off. If so, then the Australian ships are breaking the Law of the Sea, whose Article 19 specifically forbids the use of gunboat policy to challenge another nation's sovereignty.

Two, the Australian warships deliberately set a course intended to harass the Chinese navy which was in exercise and which had given advance notice of its exercise zone. If so, even though the Australian warships may well be in international waters and have "perfect right" of navigation, they displayed a total absence of professional courtesy.

Neither breaking the law nor intentional discourtesy is conduct becoming of Australia, which prides itself on supporting a rules-based international order.

Chang Wen Lam (Dr)