Would it be legitimate in the eyes of the Church if two Catholics eloped civilly prior to receiving a Catholic wedding - then later enter in to a canonically valid marriage after the 8 month waiting/marriage prep. period required by the Catholic church is over?
No, as this is considered adultery. But it's not a barrier to Catholic marriage later.
Civil marriage (as in by administrative officer) is not considered valid by C.C. I know this for a fact(s):
- Information given when attending pre-marital course as required by CC for marriage (with a host of other, very useful news).
- I know of at least two couples where this exact scenario happened: first, the civil union, then after a 6-8 months church marriage. Not sure of the penance, though.