Tempest devices could via intercepting from far away the electro-magnetic waves coming out from one's computer detect what one does on the computer. Employing the Faraday cage principle, one could prevent such detections. A. Stanoyevitch in his book Discrete Structures with Contemporary Applications, CRC Press, 2011, p.301 writes:
"Buildings can be fitted using a special insulation procedure that protects against tempest devices, but any company or individual in the US who has this insulation must first obtain a license from the federal Government."
Could this be true? If yes, which laws are involved in this context?