Three European countries face European Commission (EC) legal action after failing to enact the Markets in Financial Instruments Directive (MiFID).
MiFID came into effect on 1 November last year, but EU member states were required to implement the rules into domestic law by 31 January 2007.
In a statement, the EC said Spain, Poland and the Czech Republic failed to translate the directive into national law by the deadline.
"The provisions of MiFID have been applicable since 1 November 2007. The period of nine months between transposition into national legislation and application was intended to provide financial market participants with the required time to adapt to the new rules. The delays in transposition have shortened this period in a large majority of member states," said the statement.
MiFID aims to create a single market for investment services in Europe. But the EC added that the benefits of MiFID cannot be fully realised by European firms until all member states have complied because firms will not be able to synchronise internationally.
The case has been referred to the European Court of Justice.