Okay - my dog was a rescue dog, so wasn't a puppy. As I said I have tried pulling him away when he is weeing on grass where I don't want him to - but it makes no difference. I end up pulling him along as he is weeing! He used to wee anywhere outdoors, so does now recognise that he needs to wee on grass, but I have been unable to teach him anything beyond this.
It is easier to teach puppies, but I have never come across a dog that only wees on command. It obviously can be done, but as it is not common I think if people allow dogs into a grassy area, they should accept that dogs will wee.
I don't have a problem if pubs ban dogs in gardens because of children playing, but if dogs are allowed, then parents need to take account of that.
Just to say as well that some dogs are much harder to train than others and this never seems to be recognised. My current dog is fairly intelligent - but the dog I used to have was really thick. It genuinely seemed to be very difficult for him to remember what he was allowed and not allowed to do. He spent a lot of time looking at me confused, when I asked him to do something.
He was so thick that when we put up a conservatory he continually banged his head against the glass many many times a day - and for weeks. In the end we had to keep him out of the conservatory. It took him about 18 months of doing the same walk every day before he sussed that it was at x point we always put him back on the lead. And it was only at this point that he started to be reluctant to come to us to put him back on the lead. He was actually a fairly obedient dog once he understood what you wanted him to do. He was an absolute nightmare to train!