NYC detector bill
(NYPD Deputy Commissioner for counter terrorism)Falkenrath would not commit to publishing a list of approved devices or approved device specifications, because he said that list could give terrorists information about what the city is capable of detecting.
Vallone replied that the council normally does not pass bills with such broad language, but that he would defer to the Police Department’s judgment in this case.
So in other words, you need a permit for your detectors, but they won't tell you which detectors you'll need a permit for. Nor could manufacturers build devices to specifications for sale in NYC, because they wouldn't be able to know what those specifications were.