If someone proposes this kind of law in the US, would it be compatible with the US Constitution?

It seems to me hard to enforce in some western countries.

How can you enforce people not to buy or sell something, unless you decide it's a scam.

Regulations could be enforced, I suppose, the same way short-selling can be 'paused' in situation in which the market is going crazy or volatility is too high. But unless you use these loopholes I am not sure it would be possible.

Does anyone know of ways to enforce such a thing in the states? Or in any of the western european countries?