This is Scotland.
Plus, the guy was warned (signs) about No Photography, and ignored the warning.
Yes, it’s illegal to photograph things in many countries, like taking pictures of monuments or government buildings in Poland.
Actually, I believe most US shopping malls have rules about taking photos on mall property. It is not “illegal”, per se, but they can try to throw you out if you do it, assuming they care. I don’t believe I’ve ever seen it enforced, though.
It is private property so they can do what they want. But it’s not “illegal”.