How did the supremes know that he hadn’t simply selected ordinary soybean mutations for roundup resistance thus replicating the process (which can’t be patented) that Monsanto used to find the resistant strain in the first place? Anyone can select for anti-biotic resistant microbes. just plate bacteria on a culture with a low level of antibiotic. Take the survivors and repeat at a higher concentration of antibiotic until you have your anti-biotic resistant yersinia pestis ready to market. Same with soybeans. More expensive since you have to use a LOT of soybeans (but a lot safer), but no reason that anyone can’t do exactly that.
“How did the supremes know that he hadn’t simply selected ordinary soybean mutations for roundup resistance thus replicating the process (which can’t be patented) that Monsanto used to find the resistant strain in the first place?”
Its actually quite easy to show that the resistance was not naturally selected for by examining the sequence of the gene and the region around it.