The EU does not generally legislate packaging and labeling requirements but does so for specific high-risk products. Absent any EU-wide rules, the exporter, local partner, and/or freight forwarder should consult national regulators about packaging and labeling of containers, outside packaging, etc. EU Customs legislation only regulates administrative procedures such as: type of certificate, rule of origin on Customs forms, and shipping documents.
CE Mark: To protect consumers and end-users, EU product-specific packaging and labeling requirements exist for food, medicines, chemicals, pharmaceuticals and other items. Additionally, the CE mark is mandatory in EU countries for electrical articles. Often more than one CE mark law may apply. See: https://single-market-economy.ec.europa.eu/single-market/ce-marking_en