As kiwioaul has said take photos. Not just of the chairmans car but all cars. Then this is what I would do. I would write to the chairman saying that on advice you were told that to take further action you would need to photo evidence (digital with date stamp some smart phones don’t record the date). Then attach the photos of all cars without saying that hou know who owns which car. Tell the chairman that if the EC does not instigate a firm letter to all residents and then issue ntc to those who ignore the notice that you will take the matter further.
Now this may seem like a bluff and essentially it is. I have bluffed those on the EC here in just such a way as we had EC members who abused the visitors parking and then stating, in writing, that they could do whatever they wanted too as they apparently were more important. I let it be known that I had photos, and I wasn’t afraid to use them. Funny, the visitors car parks have been empty 99% of the time lately. Do I have photos? Yes I do. Have I taken it further? No need at the moment. All quiet on the visitor parking front – for now.