I'll add to you case. Pope John Paul the Great defined abortion as gravely immoral in Evangelium Vitae #57.
http://www.vatican.va/holy_fat...
Mind you, I think the priest should start by denying communion. And if THAT doesn't work, excommunication. Here's my question: Does Trudeau even attend Mass on a regular basis? How important is his faith if Mass isn't part of it?