Outer Space Treaty
It exclusively limits the use of the Moon and other celestial bodies to peaceful purposes and expressly prohibits their use for testing weapons of any kind, conducting military maneuvers, or establishing military bases, installations, and fortifications (Art.IV).
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The treaty explicitly forbids any government from claiming a celestial resource such as the Moon or a planet, claiming that they are the common heritage of mankind.[3] Art. II of the Treaty states that “outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means”. However, the State that launches a space object retains jurisdiction and control over that object.[4] The State is also liable for damages caused by their space object.[5]
Originally created in 1967, it’s why, when Neal Armstrong planted the US flag a couple years later, he couldn’t claim the moon for the United States!
Unfortunately I don’t know if China has signed the treaty.