3.1 Certified seeds
The seeds for sowing must be chosen from a list of varieties approved and tested at the EU level (§3.1.1). This list for hemp seeds is aimed at legally maximising the THC (psychoactive substance) content in seeds, leaves and flowers. The maximum THC content is decided by each Member State, however, in order to have the right to the CAP payments, the variety needs to have a THC content that is not higher than 0.3%.[1] Certified seeds are tested and certified according to the national protocols. In the case of the Netherlands it is the Naktuinbouw and the Council for Plant Varieties.
Collecting your own seed from a successful cultivation for a subsequent cultivation is not allowed (except for seed multiplication, which is also managed under contract). In a subsequent cultivation, the THC content could exceed the legal maximum established for CAP payments. Moreover, all hemp sowing seed must have a certificate provided by the national seed certification agency, just like for all other crops. Also, self-harvested seed might contain a higher percentage of male seed, which adversely affects the yield and harvesting process of the next harvest (see also §3.1.3). In addition, the seed might have less germination due to less sunshine hours compared to Mediterranean countries; this often too leads to lower yields.
3.1.1 EU Catalogue of varieties
[1] https://eur-lex.europa.eu/verordeningen-GLB (page 4)