any form of market manipulation is considered illegal in any country as far as i know. and pump and dump is officially a form of "fraud" which is inflating prices through false and misleading positive statements, so that the manipulator can dump what he bought at a higher price.
Could not of said it better myself and I just read up on a new type of blockchain technology developed by a group by the name of Bitcoin Origin and they have some interesting reforms on how they would prevent pump and dumps through this new technology. They plan to achieve this by implementing a Proof of Ambassador system which will require investors to supply them with certain prerequisites like Proof of Capacity,Environment,identity,stake and community.
Check them out in the link below:
https://www.bitcoinorigin.io/