Did the Second Council of Orange deny the "certain efficacy" of grace?

B. B. Warfield says in *The Plan of Salvation * \[PDF \]: > Into the place of Pelagianism there stepped at once Semipelagianism; and when the controversy with Semi-pelagianism had been fought and won, into the place of Semi-pelagianism there stepped that semi-semi-pelagianism which the Council of Orange betrayed the Church into. ... The necessity of grace had been acknowledged as the result of the Pelagian controversy: its preveniency, as the result of the Semi-pelagian controversy: but its certain efficacy, its "irresistibility" men call it, was by the fatal compromise of Orange denied. ... [After Orange it was not] any longer legally possible to ascribe salvation so entirely to the grace of God that it could complete itself without the aid of the discredited human will—its aid only as empowered and moved by prevenient grace indeed, but not effectually moved, so that it could not hold back and defeat the operations of saving grace. But I've read through the canons of the Council of Orange and I don't see how he concludes that. Is he right?