Whether it is right that schismatics should be punished with excommunication?

Objections

Objection 1 : It would seem that schismatics are not rightly punished with excommunication. For excommunication deprives a man chiefly of a share in the sacraments. But Augustine says (Contra Donat. vi, 5) that "Baptism can be received from a schismatic." Therefore it seems that excommunication is not a fitting punishment for schismatics.
Objection 2 : Further, it is the duty of Christ's faithful to lead back those who have gone astray, wherefore it is written against certain persons (Ezech. 34:4): "That which was driven away you have not brought again, neither have you sought that which was lost." Now schismatics are more easily brought back by such as may hold communion with them. Therefore it seems that they ought not to be excommunicated.
Objection 3 : Further, a double punishment is not inflicted for one and the same sin, according to Nahum 1:9: "God will not judge the same twice" [*Septuagint version]. Now some receive a temporal punishment for the sin of schism, according to Question [23], Article [5], where it is stated: "Both divine and earthly laws have laid down that those who are severed from the unity of the Church, and disturb her peace, must be punished by the secular power." Therefore they ought not to be punished with excommunication.