This is a global issue being fought in the local courts across the planet, this example being in Western Australia. In simple terms, the current interpretation is that those growing GMO crops are perfectly within their rights to contaminate the non-GMO crops of their neighbours through airborne pollination (which is how grasses pollinate). In the more extreme cases as in the United States, the interpretation is that, because of this airborne pollination, the unwitting farmer is bound to pay fees to Monsanto or their cohorts because they are using their GMO strains. The consequence of this is that those growers who wish to grow non-GMO grain, and there are many, do not have an option to do so.
When more people recognise the risks to human life from these products, perhaps this will begin to change.