The EU is already incapable of checking for cancerous substances in packages coming from China so I'm not sure how they will check for food compliance.
Yes, they are in fact hidden even better. How do you see that bananas contain banned pesticides or that meat contains banned antibiotics?
If it contains forbidden substances you fine the importer.
Most grocery chains in Germany with the exception of Edeka (I guess it's similar in other countries) apply stricter standards than the legal limit anyway with their suppliers, and ensure compliance by testing on their own