The applicants, six Spanish nationals, were owners of a parent company of RUMASA group comprised of several hundred undertakings. The Government issued a law of the expropriation in the public interest of all the shares of the company. The applicants instituted civil proceedings against the state for the restitution of the expropriated property. During the proceedings the domestic courts required the opinion of the Constitutional court. During constitutional proceedings the applicants did not have an opportunity to comment on the observations submitted by the Counsel for the State (representative of the executive authority - their opponent in the civil proceedings) or submit their own opinion.
The applicants, alleged a violation of the principle of equality of arms because their opponent in the civil proceedings, was able to submit written observations to the Constitutional court but they were not.
The Court emphasized that the principle of equality of arms was only one feature of the wider concept of a fair trial, which also included the fundamental right that proceedings should be adversarial - the parties must have an opportunity to have knowledge of and comment on the observations filed or evidence adduced by the other party. The Court noted that constitutional proceedings have their special features, however if the Constitutional court is referred to in the context of civil proceedings, persons involved in these proceedings must be guaranteed free access to the observations of the other participants in these proceedings and a genuine opportunity to comment on those observations. As the applicants were not allowed to comment on the submissions of the Counsel for the State in the proceedings before the Constitutional court, but the Counsel for the State had advance knowledge of their arguments and was able to submit his observations in full knowledge of them, the Court found a violation of the right to fair trial.