For Americans, here's the advice of the ACLU KNOW YOUR RIGHTS WHEN TAKING PHOTOS AND MAKING VIDEO AND AUDIO RECORDINGS.

It basically says you can shoot anything that happens in a public place, but in on private property, even if the public has use of the property, the owner of the property has the right to grant or withhold permission.   

I would guess(but I am not a lawyer) that this right would be assumed by anyone granted use of the property, say by rent or lease, and that right could be excercised by someone who was an agent of the owner or lessor, which would be someone that they had engaged or given permission to run a session.

Anyway, you would have had a legal right to tell video boy to stop--did he stop when you asked?