I would love to know this also. I have owned Argon for over two years, and he has pooped a grand total of once on a leash. He would rather clamp himself shut until he hurts himself (he once went three days before the vet had to get in there and fix it! :yikes: ), then poop on a leash in my presence. Let me tell you, it gets really, really old to have to take him to the dog park or daycare just to get him to poop. Argon has no offleash privledges, because he has no recall.
Even if he gets a laxative that forces him to go on leash, and we only do that with the vets ok after he's refused to go for a day or two, he won't do it next time, despite tons of praise and treats.