35 years ago in the “Les Verts” case, the #ECJ stated, for the first time, that “the European Economic Community is a Community based on the rule of law” and that neither its Member States nor its institutions could avoid a review of the conformity of their acts with the Treaty

The Green Party (Les Verts) challenged the political party funding from the European Parliament arguing that the system unlawfully favoured those parties already represented in the Parliament to the detriment of newer parties.

The #ECJ held that, the Treaty, qualified as a basic constitutional charter, established a complete system of remedies and procedures intended to entrust the Court with the control of the legality of acts of the institutions.

Thus, despite the European Parliament not appearing in the list of potential defendants laid down in Article 173 EEC Treaty, an action for annulment may lie against its measures intended to have legal effects vis-à-vis third parties.

With the ruling, the system by which the European political parties were financed was declared unlawful.
https://curia.europa.eu/juris/documents.jsf?num=294/83