As far as you know, he is permitted to grow any seed he buys. I don't understand why this is so hard for you to see. There are two elements to each of these Monsanto cases:
(i) Unsanctioned planting of Monsanto-lineage seeds
(ii) Use of glyphosphate herbicide on the resulting crop
BOTH elements are present in these cases. Not just one.
What else are people going to do with seeds, other than plant them?
And use whatever herbicide works best with these seeds, it's only best practice after all.
Since when does anybody need permission from some company before they can put a seed in the ground?
What if there is a famine, would you allow that farmer to plant the seeds, or would you happily stand by while justice has its day and these evil seeds are destroyed so that Monsanto's legally granted rights are not infringed on?
Really, the world is turning into a stranger place every day that I live in it.
I don't care how weird that sentence is, because by itself, planting unsanctioned seeds doesn't get you sued.
By all means, use whatever conventional herbicide works best on the resulting crops. Just don't spray them with the patented chemical that would kill any soybean that wasn't covered by Monsanto's patent.
The world hasn't been turned upside-down by novel applications of the law. It's been turned upside-down by massive investments in biotech that have enabled us to create magical crops that thrive despite being sprayed with extremely potent herbicides. Your argument here is an appeal to tradition and it's entirely misplaced.
I see lots of computer people do this when discussing a legal case: break it down into little pieces and then insist that each individual piece isn't a crime. (I mentally call it decomposition but law students might have a better term.) Like there must be exactly one sudden event that snaps the behavior from legal to illegal.
They are right that usually each individual piece isn't a crime. But someone can perform 15 acts, each of which, in total isolation, would be legal, but end up in a significant illegal act. As that someone performs more and more of those acts, they move from legal behavior, to probably legal behavior, probably illegal behavior, to probably illegal behavior but with minuscule damages, to illegal behavior with serious damages.
(i) Unsanctioned planting of Monsanto-lineage seeds
(ii) Use of glyphosphate herbicide on the resulting crop
BOTH elements are present in these cases. Not just one.