"Law enforcement measures against narcotics use are more severe in certain cases, such as when this use affects road safety.
"The law of 3 February 2003 17 introduced a new offence concerning any driver whose blood test reveals the presence of narcotics. These drivers risk a sentence of two years’ imprisonment and a €4,500 fine, and drivers who simultaneously use narcotics and alcohol risk up to three years' imprisonment and a €9,000 fine. The law of 18 June 1999 18 and its application decree (of 27 August 2001) 19 introduced mandatory drug use screening for drivers involved in a road accident that was immediately fatal or for drivers suspected of narcotics use who were involved in an accident that caused bodily harm. Since the 2011 adoption of the LOPPSI 2 law 20 (loi d’orientation et de programmation pour la performance de la sécurité intérieure, which covers French law enforcement activities), and its application circular of 28 March 2011, narcotics screening has become mandatory following road accidents that cause bodily harm, whether such accidents are fatal or not. Moreover, the circular 21 of 28 March 2011 on reinforcing the fight against unsafe road conditions enables, upon requisition of a French public prosecutor, random narcotics controls on all drivers (art. L.235-2 of the French Traffic Code, modified by article 83 of LOPPSI)."

Source

l'Observatoire francais des drogues et des toxicomanies (OFDT), "2012 National Report (2011 data) to the EMCDDA by the Reitox National Focal Point: France: New Development, Trends and in-depth information on selected issues (Saint-Denis, France: OFDT, 2012), p. 15.
http://www.ofdt.fr/BDD/public…