T. Lincoln Bouscaren SJ & Adam C. Ellis SJ, Canon Law: A Text and Commentary, (Milwaukee: Bruce 1946), 35. “A law may cease to bind in two ways: either by repeal, which is called extrinsic cessation, or by becoming inoperative without repeal, which is called intrinsic cessation. It is common doctrine that a law ceases to bind without repeal in two cases: first, if the circuмstances are such that the law has become positively harmful or unreasonable; second, if the purpose of the law has entirely ceased for the entire community.”
So Fr. Cekada has the Leonine Prayers ceasing to bind because either those prayers have "become positively harmful or unreasonable," or "the purpose of the law has entirely ceased for the entire community."
Or ...
He just doesn't want to say the prayers because he'd like to do his own thing.