I think EU and US should get together.
For designated components buying/preordering more than X$ or 2 months projected supply, whichever is larger, of a component should be forbidden. All distributors should be licensed to not sell for more than X% over manufacturer quoted prices for given order size, buying from an unlicensed distributor forbidden.
I would rather over pay for genuine parts.
We are in a market shortage situation right now. If people are hoarding parts because they fear they will run out, the price for the parts is too low. You cannot fix this any other way but let Digi-Key, Mouser, etc. charge actual market price for these parts. This is not exploitative, it's just market economics.
If this means $25 STM32's then that's the price ... but this will also mean you have a legitimate, traceable way to get parts. It will also shift demand to parts that are in good supply or made with fabs that have plenty of capacity.
And the prices will come down once more supply comes on-line, and this would lead to a cooling of the market. Forget about trying to prevent hoarding, it just is not going to be possible. Some of these parts resellers are buying from people who just have garages full of parts.