I've had the same problem so to speak. Dogs fouling on the footpath outside of my house and in my front garden.
I contacted my local council through this website....
http://www.fixmystreet.com/I received an email the following day from my council. I wanted to clarify with the council that i would not be contravening any by laws if i erected posters on wooden boards in my front garden making dog walkers aware that their dog poo was not welcome on the public foot path outside my home and on my property. The council were absolutely fine with this. I also spoke to my neighbours as neither of them have dogs and i didn't want offend them but i'm glad to say they were all for it.
It has to be said there has been no poo since the signs went up but i suspect the offenders may have changed their walking route.
This is what i wrote on my poster, A4 size....
DOES THIS BELONG TO YOU?
Dear dog owner,
Almost every day now I find a pile like this on the pavement outside my house and my neighbour's house. It always seems to have come from the same dog? Is that your dog?
Not only is it against the law, your dog waste doesn't disappear by magic. I clean it up.
IF YOU CAN'T CLEAN UP AFTER YOUR DOG YOU SHOULDN'T HAVE A DOG - SIMPLE!
Please take responsibility for your dog, it doesn't know any better. YOU SHOULD DO!
PICK UP AFTER YOUR DOG!!!
I went to google images and found some very good posters which have been used by various councils up and down the country.
I hope you find a solution soon.