https://en.wikipedia.org/wiki/Monsanto_Canada_Inc_v_Schmeiser is the notable case. Monsanto has somehow never lost a case, but this defendant was deemed not liable.
Monsanto will happily remove entire crops affected by their stuff... but that's removing and destroying entire crops. That's not a small thing to a farmer. And if you don't and don't pay them a licence fee, then they are quite happy to follow through with litigation.