The FCC (Federal Communications Commission) does not "own" space in some divine way, instead it is the US agency that issues licences for transmissions at certain powers and certain frequencies, and it may act to interdict unlicensed transmissions that cause interference to receivers of permitted transmissions (and radio astronomers). The questioner asks about radio frequency equipment that is so thoroughly screened that there is no transmission and that would be no concern of the FCC. In the case of frequencies that went unused after the change of analog TV signal to digital the FCC have expressly relinquished control.
http://www.cnet.com/news/fcc-opens-free-white-space-spectrum/
However the activities described if discovered would likely attract negative attention from authorities in countries with little or no tradition for amateur radio, notably Iran, Yemen and North Korea.