A number of people have responded to the key points, but one that hasn't been mentioned is that we have a presumption of innocence. So if a UAV shows up, and you're holding a .45 caliber handgun, we still have to presume you are innocent of the shooting (you may have picked up the gun from the street for example). However, if you take aim at a UAV streaming video back to base and start shooting at it, well that can and will be used against you in a court of law.
There is another issue which is that a hand gun is a poor weapon for shooting down an aerial vehicle. A good marksman, or someone very lucky might do it, but the weapon of choice would be a shotgun. Shot guns on the other hand are not effective at range so in a street fight they aren't a good weapon (great for close quarters, poor for engaging at range).
So in a completely lawless sort of situation I could see teams of shotgun toting folks keeping the UAV population down but not in the typical urban setting in the US.
If camera toting quadcopters on microphone equipped poles become common, I'd expect West Oakland gangs to start handing out high powered laser pointers to all the local kids…
Well I don't know about low light, but lasers operate on very narrow color bands, so if you filter out the color of the laser in the video stream, you filter out most of the laser light. You also have to be very precise to actually hit that tiny sensor moving in the air from a distance.
Just so you know, shotguns are not the wildly inaccurate things as depicted in most TV shows and video games. Depending on the choke and ammo used, they can be accurate up to 50yds with Buckshot (depending on choke), and probably up to 100yds with slugs.
I would say the most damning thing about using them for the purposes you describe would be the awkwardness of carrying around a shotgun that is that accurate and hiding it.
There is another issue which is that a hand gun is a poor weapon for shooting down an aerial vehicle. A good marksman, or someone very lucky might do it, but the weapon of choice would be a shotgun. Shot guns on the other hand are not effective at range so in a street fight they aren't a good weapon (great for close quarters, poor for engaging at range).
So in a completely lawless sort of situation I could see teams of shotgun toting folks keeping the UAV population down but not in the typical urban setting in the US.