Brussels has said that France has yet to write Directive 98/5/EC on the establishment of lawyers into its national laws, despite an ECJ ruling last September that it should do so. In June, the commission could ask ECJ judges to levy fines until the French government complies.
The fines could prove expensive. In 2001, for example, the Greek government was forced to pay €4.78m for failing to clean up a (£3.05m) toxic waste dump in Crete.
France has been given two months to state how it will introduce the directive, or face an application at the court for a fine.
The legislation allows EU lawyers to begin practising in another member state under the professional title earned in their home country, without undertaking a test or a period of adaptation. Within three years they can acquire the professional title of the host country.