Final answer:
The ECJ considered the balance between environmental benefits and negative impacts, the reasonable transitional period, the ability of all producers to participate, the importance of the environmental goal, and the impact on importers in determining the compliance of the national rule with the principle of proportionality.
Step-by-step explanation:
The key factors and principles that the ECJ considered in determining the compliance of the national rule with the principle of proportionality were:
- The balance between environmental benefits and negative impacts on non-German producers;
- The reasonable transitional period given to producers and distributors to adapt their production methods;
- The ability for every producer or distributor to participate in the new system by the time it takes effect;
- The importance of the environmental goal served by the rules;
- The impact on importers, even if it was greater, as long as it was in line with the principle of proportionality.