Article 174 of the French Code of Criminal Procedure
When a case is referred to the Investigating Chamber on the basis of Article 173 or Article 221-3, all pleas alleging the invalidity of the proceedings referred to it must, without prejudice to its right to raise them of its own motion, be submitted to it. Failing this, the parties shall no longer be entitled to raise them, except in cases where they could not have been aware of them….