[Campion]

A pope is only infallible when he says he is infallible.

That isn't quite true. Vatican Council I set down 4 conditions for an infallible Papal teaching:

• The Pope must be speaking in his supreme authority as Pope, not as a private teacher, as Bishop of Rome, etc.
• He must be speaking to the whole church. An interview with a journalist flunks this test, as does a decree disciplining a particular individual.
• He must be attempting to teach definitively, as something Catholics are required to believe under pain of heresy
• And he must be teaching a doctrine concerning faith or morals. Musings concerning, e.g., science or baseball don't count.

[impimp]

Yes...but he also has to say he is acting infallibly. The wording was clear with the assumption. It was also clear when the bishops conference was ratified- i.e. Vatican 2.