Article R2393-4 of the French Public procurement code
When the purchaser decides to require the holder, for all or some of the subcontracts, to put the economic operators out to tender in order to choose one or more subcontractors pursuant to 1° of Article L. 2393-3, it shall state this in the contract notice. Where appropriate, the purchaser shall also identify in this notice the essential tasks that may not be subcontracted pursuant to Article L. 2393-7.