Yes he is.
Can. 1315 §1 Whoever has legislative power can also make penal laws. A legislator can, however, by laws of his own, reinforce with a fitting penalty a divine law or an ecclesiastical law of a higher authority, observing the limits of his competence in respect of territory or persons.§2 A law can either itself determine the penalty or leave its determination to the prudent decision of a judge.
§3 A particular law can also add other penalties to those laid down for a certain offence in a universal law; this is not to be done, however, except for the gravest necessity. If a universal law threatens an undetermined penalty or a discretionary penalty, a particular law can establish in its place a determined or an obligatory penalty.
This is Bruskewitz' justification? I'd like to see more substantiation that this empowers him to apply excommunication, willy-nilly.