No federal laws against them, you could build a fence or something non structural most places. There is not a single National code in the US.
The heads are smaller so they are more likely to pull through structural, roof sheathing etc. In many locals along the South and East coast they are either against code or frowned upon due to hurricane wind threat. In California/ west coast due to earthquakes again they are more likely to pull through sheathing in a quake.
Probably in the central US in "tornado alley" they have or will have in the future problems with them too.
Here in Georgia I dont think I can even buy clipped head nails or nailers at my local big boxes stores.
Thanks again,
Brad