Here's the case I was thinking of (it was canola, not soybeans):
https://decisions.fct-cf.gc.ca/fc-cf/decisions/en/item/38991...
As for Bowman
https://www.supremecourt.gov/opinions/12pdf/11-796_c07d.pdf
Bowman didn't just do that. He applied glyphosate to the field. So, he bought seeds without a license to grow them, with the intent to exploit the fact they were resistant to glyphosate. This violated the patent.
> GMO IP protection does nothing to prevent farmers from continuing to grow previously existing varieties.
If they buy seed from grain elevator which comingles GMO and non-GMO seed (which is what happened in the Bowman case) the farmer can't sell what they've grown from that seed.