The EU rules for "organic" are complex, but the principle is that "organic" is a way or producing food, not a test done on food after it has been produced.
The orginal notion was to produce vegetables without using mineral fertilizers or pesticides, and instead depend on compost or manure as fertilizer. This was then extended to Livestock and Aquaculture, and even to non-food products, such as cosmetics. To get organic certification you need to prove (usually through a body such as the Soil Association) that you are compliant with all the rules for "Organic". This means lots of paperwork!
If you can prove through the certification process that you are producing food in an organic way, then your produce can bear the "organic" label. It is not based on a test of the food. See Ecocert for more details of the certification procedure.