The size of strawberries for sale in shops is decided by the European Commission in a regulation ”binding in its entirety and directly applicable in all Member States”.
The national parliaments or the European Parliament cannot change such rules. It is one of 80,000 rules which cannot be changed by the voters.
According to an EU-regulation (EC No 843/2002 May 21 2002) it is illegal to sell strawberries measuring less than 18 mm in diameter. The detalied EU-rules applies to strawberries sold in shops and in local markets. It is possible to sell strawberries with a smaller diameter for industrial production of jam.
Strawberries in "Extra" class must be at least 25 mm in diameter. Classes I and II 18 mm. There is no minimum size for wild strawberries.
The EU has different rules on the size and quality of most fruit. It is now permitted to sell cucumbers not respecting the EU rules on their curvature. The reform of the market for fruit and vegetables n 2009 did not reform the rules for the sale of all fruits.
The EU has anti-dumping-duties on the import of frozen strawberries from China.