Regulations of Tempest protection of buildings
<p>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:</p>

<p>"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."</p>

<p>Could this be true? If yes, which laws are involved in this context?</p>

<p>The only applicable law for the US would seem to be FCC regulations against interfering with "any radio communications of any station licensed or authorized". <a href="https://apps.fcc.gov/edocs_public/attachmatch/DA-14-1444A1_Rcd.pdf" rel="nofollow noreferrer">Marriott Hotels</a> was fined substantially for blocking people's hotspots within the hotel. As I understand "tempest device", this is a method of obtaining information from stray EMR from computers and the like, which picks up on radiation emitted from a device. Stray radiation is not licensed communication. The problem would be if a room were insulated to block all EM radiation coming in or going out, including licensed transmissions. The main enforcement interest of FCC is with devices that actively jam signals (by transmitting interference). But the law, <a href="https://www.law.cornell.edu/uscode/text/47/333" rel="nofollow noreferrer">47 USC 333</a>, states that "No person shall willfully or maliciously interfere with or cause interference to any radio communications of any station licensed or authorized by or under this chapter or operated by the United States Government". Insulating a room from incoming licensed radio signals is thus not allowed, under a "what the law says" reading of the law. However, laws are frequently interpreted in terms of beliefs about an intent, so it's possible that a court could eventually decide that the law was not intended to prevent construction of a Faraday cage room. The issue would then be whether an intentional action to do something allowed which has an (unintended) disallowed but non-harmful consequence would be deemed a violation (the user would be okay with blocking licensed transmissions into the room). I don't know of clearly applicable case law on that point.</p>

united-states privacy hacking search-and-seizure regulations