formal and substantial irregularity of procedural acts in french law

procedural acts may be invalid because of formal or substantial irregularity. in french procedural law, we can see a distinction between invalidity of instruments owning to formal irregularity and invalidity of documents by reason of essential defect; a distinction that affects the nature and plea time and the subsequent regularization of document. formal invalidity must be expressly provided in law, except where it is a case of a failure to comply with an important formality or one of public policies, but plea of invalidity based on failure to comply with substantive rules relating to written pleadings shall be admissible without the party raising them having to prove any prejudice to him even where the invalidity does not arise under express provisions.