English Heritage claims it owns every single image of Stonehenge, ever

SteveMars sez, "Every photo image library got this by email today. 'We are sending you an email regarding images of Stonehenge in your fotoLibra website. Please be aware that any images of Stonehenge can not be used for any commercial interest, all commercial interest to sell images must be directed to English Heritage.' Here is one image library's response:"

It's kind of them to think of us, but this raises a number of questions.

Firstly, what legitimacy do they have for this claim? Is there any law that states that it is illegal to use images of Stonehenge for any commercial interest? Can someone direct me to it?

Secondly, if an image of Stonehenge is so used, how could they possibly police the usage? A quick browse through a number of rights-managed and royalty-free online picture libraries produced the following:

iStockPhoto (a US owned company) has 513 images of Stonehenge
Fotolia (US) has 648 images of Stonehenge
Dreamstime (US) has 670 images of Stonehenge
Shutterstock (US) has 737 images of Stonehenge

All the above sites sell images on a royalty free, unrestricted usage basis. If anyone buys a royalty free image from one of these suppliers then he'll be using it as, where and when he likes, without asking English Heritage's permission. How will they stop that?

Stonewalling Stonehenge

(Thanks, SteveMars, via Submitterator!)