Quatro Security acting illegally

Quatro Security is preventing my partner from entering our estate based solely on the request of our neighbor, who happens to be the head of the body corporate. On 2 occasions the police had to called when they tried to evict him from our house, and where they indicated that this is illegal. Quatro Security again tried to prevent him from entering the estate. Spoke to their supervisor - Oscar - who said they were simply following their clients instructions, even though it is illegal.