Secondly if the Law cuм ex was cited in the 1917 Code, then cite it. I have the 1917 Code of Canon Law in 2 different commentaries and it does not mention cuм Ex at all. Furthermore it states the same decree that Pope St. Pius X made and was cited by Ecclesia Militans.
I believe you have recieved faulty information.
I just wanted to post here that "cuм Ex" is cited in the footnotes referring to Canon 188.4 which, I think, deals with the loss of office due to the defection from the faith.
The copy I am referring to was published by PJ Kennedy and Sons, in 1918 and the text in reference is located on p. 47. If a scan is requested, I can probably come up with that. Either way, I am doing this to support Thursday and KofCTrad.
Also, St. Thomas refers to an act of worship that is directed to an end that is not God is an act of apostasy (worshiping at the tomb of Mahomet is the example).
These men (Paul VI, JPII, B16) have done far worse - not only engaging in false worship, they have promoted it among their hierarchy and forced it on the faithful and encouraged members of false religions to continue and promote their false religions. They have taken part in pagan, muslim and judaic worship.
It really is not complex - they are not Catholics.