@ AC 12:03
"It's not that simple. What, exactly, would one ban? A ban that is easily circumvented by the vendors changing how the device is described would be annoying and pointless. Suppose, for example, that the vendor offers a generic sound-producing device that can be programmed to do lots of different things, including the "mosquito" function."
Well, that's so easily dealt with I'm surprised it even needs saying. A device incorporating an illegal function is illegal, surely. You don't say "That handgun is legal because it also includes a torch" do you? Or do you?
"The comparison with blocking mobile phones is rubbish: it is not "legal to transmit signals". In general, it is illegal to operate any radio transmitter. There are specific exceptions for licensed devices such as mobile phones."
No it's not. My original point might have been a simplification, but in essence it is possible, as you have demonstrated, to licence certain use of a technology without giving carte blanche. Allowing people to have sound-generating equipment (a hi-fi) does not mean you have to allow them to play nuisance sound to drive people away from a location. And you don't have to frame the law such that nuisance has to to be demonstrated in each instance, merely ban the devices which have that function. Can't own it, can't operate it.