Question juridique clé
Whether the non-communication of a spontaneous reply violated the appellants' right to be heard.
Solution extraite
Yes. Any new submission admitted by the court must be communicated to the opposing party so it can decide whether to comment, even if it appears immaterial.
Motifs extraits
The cantonal court admitted the spontaneous reply and relied on it, yet failed to transmit it to the appellants. This deprived them of the opportunity to respond. The violation could not be cured before the Federal Court.