Earlier quoted context omitted.
If you get trespassed then wouldn't the police get involved?
Depends on the laws in Belgium (I've no idea what they are)... in the UK for example trespass by itself is not a criminal matter, even if somebody refuses to leave your property... they need to be doing something else.
In this case the Belgian police might have been justified in escorting the journalists off the premises. But I'm not sure what grounds they had to detain and question them.