To avoid the economic consequences of admixtures of genetically modified (GM) and non-GM harvests, and to ensure that agricultural production complies with mandatory labeling provisions, the European Union (EU; Brussels) member states have adopted co-existence measures directed to farmers cultivating GM varieties. For GM maize cultivation, regulators have established mandatory isolation distances, which differ between countries and in some cases have been regarded as disproportionate. Taking advantage of numerous field studies conducted by EU researchers in recent years, we report here a statistical analysis of crossfertilization data in maize, showing that separating fields 40 m is sufficient to keep GM adventitious presence below the legal labeling threshold in the EU set at 0.9%.