Personally, it wouldn't bother me one bit if they just outlawed all the chemical fertilizers and such. Nobody needs "perfect" or "better than the Jones's" lawns.
My lawns never been perfect but they banned "Cosmetic" herbicide use here in Ontario a couple years ago. Basically, you can't spray your lawn. A lot of people were pretty upset and a bunch just do it anyway. Biggest thing I've noticed is public parks are pretty weedy now but otherwise, no big deal. I do find it frustrating that golf courses are exempt because they are a "business" and they are one of the largest users of weed control products and fertilizers.
I worked in formulation screening for a major ag chem company for many years and I can tell you that most of the products on the market today are pretty safe when used properly. Most farmers use them wisely because they are looking to maximize profit and chemicals are expensive so any way they can reduce product reduces cost. Homeowners don't think this way and usually over do their applications.
Here we can get our water report that lists what major ag chemicals are in the water. Mine's pretty good but not perfect. Atrazine is an older chemical with a long soil life that used to be used in large volumes. It's been replaced by newer products that don't have the carry-over concerns but it's still hanging around. Like mentioned before, the bigger concern is ground water nitrate levels which can lead to all kinds of problems.
I am also amazed at how much water is used on lawns in general. Groundwater is dwindling in a lot of areas but people still water. Where I live, we've always had a low volume municipal well and no one can water. Everyone's lawns look like crap in August, no one cares. It's just a lawn. I'll spend my time being proud of my kids or my beer before I worry about being proud of my lawn...