Where do you live that spraying herbicide on someone else's garden isn't considered tresspassing and destroying private property?
Maybe it is, but on the other hand he knew his "garden" (containers with weeds in them) were a nuisance to the neighbors. Litigation is often possible while at the same time not really the coolest thing to do.
I have no idea why you were down voted because that was exactly my reasoning :-) I live in rural Japan. I admit that while I was really angry about someone just coming in and pouring herbicide on my plants, I was more upset that someone didn't just come and talk to me about it. But that's Japanese culture and in retrospect I should have been a bit more outgoing in trying to explain to people what I was doing. In the end I screamed at the gas man from half way across the neighbourhood and he was so embarrassed that he ended up having to transfer to a different part of the city. It probably sounds strange, but I still feel really bad about that. He ruined my 5 year long experiment and killed my plants, but at the time I was yelling at him, it was already done. Hurting him in order to satisfy my anger doesn't actually improve the situation.
Edit: I should point out in my own defence that I didn't actually realize ahead of time that my planters were a nuisance. I weeded out all noxious weeds and my containers were fairly well isolated with about 10 feet of concrete in every direction. Also, there was a parking lot on one side of my lot and an orchard with about a foot of mulch on the ground on the other. The spread of weeds should not have concerned anyone. I honestly think they thought I had just abandoned the planters. It's too bad, but a lesson for me in the importance of optics when you do hair brained experiments at home ;-)
There is some controversy over whether he really got the kinds of yields he reported with the kind of work he said he did. Part of the problem was that he got really famous and people would wander over and help him out for a while so that they could learn his techniques. However, I have a friend who studied with him and I can report that he literally does manage to feed himself and his wife all of their fruit and vegetables and only spend some of his spare time (he is a high school teacher by trade). The biggest piece of labour is cutting the rice, which takes several days (and which he does all by hand).
When I visited his fields (in Japan), it had been a bad year that had been compounded by a typhoon just before harvest. My friend's field was in great shape while you could see that the neighbours had lost at least 20% of their crop. It was also really interesting to see the difference in wildlife diversity between the fields. These fields were very small (about the size of a large house lot in the US) and my friend's lot was full of frogs, snakes and spiders, while the neighbour's had nothing in them but rice. My friend said that his neighbour usually produces more rice than he does, but that his field is always much better in a bad year.
I actually did a 5 year experiment trying to grow food in containers with no inputs other than water. You need fairly big containers (depth is the most important thing), but I was surprised how well it worked. At the end of the 5 years I was getting pretty good yields with virtually no work and no inputs. In the end I had to give up because while the containers grew a lot of food, they also grew a lot of weeds. The neighbours didn't understand and one day I got home to find the gas man spraying herbicide on everything. Everybody thought it was an eyesore and he was delegated to "fix" the problem. :-P
In any case, my experience makes me think that there is room for some research in farming where we don't try to micro-manage everything.