This is reductive to the point of misleading. France does control its borders, but has chosen to accept the freedom of movement of Schengen, become a party to the Dublin Regulation, and participate in Frontex.
The idea that France is helpless to deal with the question of how it treats the migrants and the asylum seekers within its borders because of these agreements is to absolve them of responsibility towards people that they have taken on through those choices in addition to their own domestic law.
Telling people they can't work at all in your country, when they have nowhere else to go, is cruel. That is a choice France -- and other countries like Germany -- have made, and should be held responsible for.
(PS, I also disagree with the characterisation of the European borders as 'porous', given how much money, manpower, and how many human lives are expended enforcing them. If they were porous, people would not be drowning in the Mediterranean trying to reach Europe.)