Here is parts of the article I posted regarding the legality of the use of emf shielding. Read it carefully, and I suggest you also read the posted document in full as well. This poses many problems to the public in general, and the private sector in specific. PERRY, I suggest you read this.
NACSIM 5100A is classified, as are all details of TEMPEST.
The information may be classified, as perhaps it should be. If I were an organization of any kind trying to protect my data I wouldn't run around publicizing the details of the technology required to protect it either. This does not mean though, that it is illegal to reinvent the wheel and apply it yourself. Besides, who is to say what is an "acceptable" level of EM radiation - the government has clearly chosen what it considers acceptable levels to facilitate equipment supply by contractors. If you want more or less protection then you and any other member of the public are free to define, manufacture or purchase whatever you want. And if you can't get it from a local source I am sure there are plenty of governments and manufacturers elsewhere in the world you can deal with, though of course exporting the technology may be another matter, but there is nothing new about that. There are plenty of other government conspiracies to focus on ! This one seems a bit lame. david