Beijing's response to the US shooting down its balloon has been muted. It might be China's way of preparing for a future in which the roles are reversed, says international law expert.

• China has to consider what it will do if the US sends balloons into Chinese airspace, a legal expert said.
• The US shot down what it described as a Chinese "surveillance balloon" on Saturday.
• If Beijing pushes too hard on its response, its own rhetoric may backfire later, Julian Ku told NYT.

As Beijing calculates its full response to its balloon being shot down off the southeastern US coast on Saturday, it needs to consider what it will do if the US starts sending balloons to China, an international law expert said.