The operative standard is called a precautionary principle, which loosely translates as guilty until proven innocent. No scientific evidence is needed for banning commodity imports, as mandated by other international trade agreements. For anyone watching, it is hard to tell what the fight is about. Little of the dispute is rooted in demonstrated concerns about public health.
Economic chauvinism is as much a predictor of behavior as scientific doubt.
Intellectual property rights and royalty payments for U.S. firms upset the Europeans as much or more than the creation of so-called Frankenfoods. No one is holding Europeans accountable for their current levels of pesticide use and other risky applications that biotechnology might be able to dramatically reduce. At this point, GMOs loom as a greater threat to established political and economic interests abroad, so the underlying objections are rooted in culture and not science. So far, the pattern is interference without rigorous examination. Science is ignored and emotions are exploited to restrict imports and overseas competition.