Yes, it looks like this has been covered well. 8 weeks is pretty standard in most states. There is no enforcement of this age either, except in the case of shipping pups, when a USDA certificate is needed, which is at least 8 wks.
Personally, I find puppies, Newf pups, do better if held on until 10 wks of age. That little bit of maturity makes a big difference in terms of their new home adjustment, potty training, fear periods, etc. Plus, a breeder can obtain at least one cardio check, although many innocent murmurs will still be audible at 10 wks.
Interestingly,The Blind School, in New Jersey, I believe, trained mostly Goldens, and Labs, and actually bred them right on site. After many tests, and studies, felt the best age to "foster" the pups out to their training homes, prior to formal training, and ultimate placement, was 7 weeks of age. They felt that 8 wks was a big fear period.
Of course, this was primarily for Labs and Goldens, perhaps a few German Shepherds.
Not Newfs.