This is nothing new, this goes for every device with WiFi.
The European version of Apple products, such as the iPhone, follows European regulations and is certified by a European authority the same way that the FCC certifies compliance with US regulations.
If the device is certified by the FCC, it has a FCC logo on the back (or bottom) and if it complies with European regulations it has a EC logo. The iPhone sold in Europe has both the FCC and EC logo as it complies with both.
Customs officials only need to check for the EC logo to see if it is in compliance with European regulations or not.
But it cuts both ways. The EU requires weaker transmitters but allows for more channels than the US so a WiFi device designed to make the most of the EU standard could very well get confiscated by US customs as it would contains a WiFi transmitter not in compliance with FCC regulations - and you know how strict the the US is about FCC compliance.
UPDATE: now that I look at the photos of the US iPad, it looks like it has a CE0682 logo next to the FCC logo. That should mean the current iPad is an international model and the only one there is going to be and that it complies with EU radio transmitter regulations.
Fortunately, we've already established that.