... now we just need to figure out how to lure the surveillance target into our EM-shielded cage.
my point is that it's quite easy to "play" with such things without actually breaking the law
They aren't "playing".
I think you may have misunderstood the comment. In the US, Ireland, and probably elsewhere, police are using rogue cell sites ("Stingrays") for surveillance. The person you replied to is claiming that this is illegal, and the police forces that are doing it should be punished. They weren't talking about people experimenting with setting up Faraday-caged toy cell sites in their basement — there's absolutely nothing wrong with that and it should be encouraged!
the executives and owners of Harris in jail
They were also talking about the people that built the devices.
Did you intend to reply to the grandparent comment?