I am just wondering what are the legal limits to the extent to which private security can use physical force?
For example, if I am in a private establishment (let's say, a shopping mall); a security guard asks to me to leave and I refuse. Is he legally allowed to beat me up and break my arm?
Another example, if I am on a facility owned by a private company and a security guard asks me to hand over my cell phone and I refuse - can he beat me up and take it?
More extreme examples might be if I was damaging property or trying to harm someone on the private premises. I would assume private security would have some powers to use force to defend people/property from damage?
In terms of jurisdictions, it is US/UK I am primarily interested in.