Monsanto has won a legal battle against a Canadian farmer it accused of growing a form of genetically modified rapeseed it had patented without paying for it.
Rapeseed is used as animal feed
Canada's Supreme Court on Friday ruled that Percy Schmeiser, who was found to be growing the GM rapeseed in 1998, had breached Monsanto's patent.
He had denied planting Monsanto seeds, saying they took root on his land through natural cross-pollination.
The case became a cause celebre among opponents of GM crops.
They claimed that a decision in Monsanto's favour would expose all farmers whose crops became accidentally pollinated by GM plants to lawsuits.
They also argued that farmers wishing to market their grain as non-GM would be deterred from complaining if their crops became contaminated by GM plants.
Monsanto argued in court that the proportion of GM seed growing on Mr Schmeiser's land was so high that it was more likely he planted it himself.
The Supreme Court ordered Mr Schmeiser to surrender any remaining GM plants and seeds in his possession to Monsanto.
Schmeiser will not lose his 1998 profits
But it threw out a lower court ruling ordering Mr Schmeiser to pay the profits of his 1998 crop - about 20,000 Canadian dollars ($14,500) - to Monsanto in compensation.
Monsanto welcomed the Supreme Court's decision.
"This ruling maintains Canada as an attractive investment opportunity," it said in a statement.
"Patent protection encourages innovations that will lead to the next generation of value-added products for Canadian farmers."
Monsanto's "Roundup Ready" rapeseed - genetically engineered to resist a powerful herbicide - accounts for about 40% of Canada's rapeseed crop.
It enables farmers to use the weedkiller at a time and in a quantity that would not be possible with traditional varieties of rapeseed, increasing their crop yield.
Earlier this month, Monsanto shelved plans to introduce a Roundup Ready variety of wheat, amid fears that consumer resistance to the crop - particularly in Europe - would be too strong to overcome.
Rapeseed - known as canola in North America - is used as animal feed and as a source of vegetable oil.