Sure but that doesn't include shutting down Telegram. It is easy enough to infiltrate those groups and keep them under surveillance. You can do very basic police work to counter act them.
Infiltration also isn't as easy as it sounds. They can use that as a defense. Which actually happend several years ago. They failed to get rid of the NPD, a Neo-Nazi party, because they couldn't be sure if their plans were legit.
https://en.wikipedia.org/wiki/National_Democratic_Party_of_G...
Getting a company to obey the law is probably easier.