I don't know what are the exact laws, but they sure do not make you in your right to agress someone in your property if he does not follow your rules, even if the rules are backed by the law.
The thing I am sure however, is that you will inevitably end up in trouble if you attack someone for whatever reason, even if he is in your property.
And here we are not speaking about the right of self defense, which is by the law authorized if :
- actual danger
- injustified aggression
- real aggression (a simple threat is not enough)
- the defense used must be the only way to defend oneself
- proportionnal to aggression (no excess tolerated)
So, no. I wonder what the aggressors were thinking. And anyway, this is not even their property, its Mac Donald property, and I am pretty sure their policies are slightly different. :3