You are thinking of https://en.wikipedia.org/wiki/Monsanto_Canada_Inc_v_Schmeise.... He is often heralded by anti-GMO activists as an example of the dangers of GMOs and Monsanto, but the fact of the matter is that the "cross contamination" is a myth. He deliberately took cultivars from his neighbour's plot and analysis showed that they comprised a significant portion of his crops, which wouldn't be possible by cross-pollination alone.
Should seeds be patented? Are Bayer, Monsanto, Syngenta, and agrochemicals companies evil? These are all worth discussing (the answer to the second question is yes), but that particular myth is not.