Article R2393-7 of the French Public procurement code
When the purchaser decides to require the contractor to subcontract part of his contract pursuant to 2° of article L. 2393-3, he shall indicate this in the contract notice in the form of percentages set under the conditions laid down in article R. 2393-8. Where applicable, it also identifies in this notice the essential tasks that cannot be subcontracted in application of article L. 2393-7.