Derek, the only reson i can think of is perhaps it's more being inside a security restricted area... for example, in Customs/Passport Control in Aus airports, you are not allowed to use a mobile phone, camera or other recording device. Perhaps this is what was meant at your particular location as well???
I once saw a guy havng a very loud conversation on his phone right under the sign with a big picture of a phone and a slash mark through it, and the words "$10,000", wish I'd had a camera with me, hahah, or been allowed to use one!!
