If Argentina has such laws, they are breaking treaties that the country has signed.
The claims about farmers inadvertently using Monsanto seeds are rubbish. If some seeds would spread like wildfire, that would be a different thing. But they don't. The farmers using Monsanto (and any other licensed) seeds are doing it on purpose.
The most commonly cited claim here is Monsanto vs. Schmeiser, and you should read it:
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"If you don't like Monsanto's work, don't pirate it. "
Their (plant)-technology infiltrates the environment around, so at the end of the day, all farmers are using some kind of monsatos tech (unwanted).
Should they pay, because monsatos IP is spreading like a wildfire?
no offense & best regards