Outside should be exempted.
I also disagree the law states smoking areas should be clearly defined and segregate, as most terraces have some form of roof there is no true ventilation as smoke rises, if the terrace area is smoking only then the restaurant is restricting non smokers to dine inside, which is against consumer rights.
It's from the UK interesting reading about the risks of second hand smoke [ash.org.uk/files/documents/ASH_827.pdf]