Illegal Picture?

Not so long ago I was told off in a public place for taking pictures in an area where there are other children. It was explained to me that it was due to the Child Protection Act of 19xx or something it was basically illegal to take pictures of other people's children (regardless of the fact that I had positioned the shot so that there weree no other children other than my own in front of me!). I wasn't really listening to the detail, really. I was more annoyed that I was being told off over the tannoy system. Nevertheless, I kept taking pictures and wasn't arrested.

I'm sure that there is no Act or Law that explicitly says that you cannot take pictures where other peoples children may get in shot. Even if there was, I wonder if such law could ever extend to taking pictures of other people's children's shadows?