This really is not as huge as it may appear.
Brazil has many worthy consumer protections enshrined in law, however, when it comes to policing them? There is either no one person or organization tasked with responsibility for policing the laws, or the agency responsible is so corrupt that it makes no difference.
Rio Grand Do Sul is probably the largest soy bean producing state and all soy bean, GMO or otherwise, is sent to to one central hub and is all mixed together regardless.
Brazil has food labelling laws that decree that all GMO ingredients are listed on the packaging, but it is only the large, multi national conglomerates that do this and, again, there is no one to police it.
Maybe, hopefully, things are going to change there as well.