A good friend of mine sent me this link earlier, which I thought was important to share as we have all been in the situations shown in this video. A lot of photographer are completely unaware of their rights when shooting in public places, be it street photography, architectural photography or even just shooting there friends and then having trouble with security guards, locals, etc.
Of course you must remember that shooting in private spaces, i.e. shopping malls, etc the rules are different.
Video Link: Stand your ground