1917 Code 1070 and 1098 in particular. I cited it above, but I deleted the cross-references to the 1983 Code, but the latter upholds the same standards ... EXCEPT that at some point that I not yet researched, one of the Conciliar papal claimants made an exception for those who formally renounced their Catholic faith. But that caused so much confusion that in 2009 Ratzinger rolled it back.
Referencing Ott who referenced the Council of Trent.....
Trent:
Although it is not to be doubted, that clandestine marriages, made with the free consent of the contracting parties, are valid and true marriages, so long as the Church has not rendered them invalid; and consequently, that those persons are justly to be condemned, as the holy Synod doth condemn them with anathema, who deny that such marriages are true and valid; as also those who falsely affirm that marriages contracted by the children of a family, without the consent of their parents, are invalid, and that parents can make such marriages either valid or invalid; nevertheless...
Trent then goes on to talk about those *not* free to marry:
....and whereas it takes into account the grievous sins which arise from the said clandestine marriages, and especially the sins of those parties who live on in a state of damnation, when, having left their former wife, with whom they had contracted marriage secretly, they publicly marry another, and with her live in perpetual adultery; an evil which the Church, which judges not of what is hidden, cannot rectify, unless some more efficacious remedy be applied....
....Those who shall attempt to contract marriage otherwise than in the presence of the parish priest, or of some other priest by permission of the said parish priest, or of the Ordinary, and in the presence of two or three witnesses; the holy Synod renders such wholly incapable of thus contracting and declares such contracts invalid and null, as by the present decree It invalidates and annuls them.
For those *free to marry* but marry outside of the Church, their marriage is valid unless and until the Church declares them invalid. Is that not what Trent says above in bold?
This is something I've come across more than once, there is a dreadful misconception among trads that all marriages outside of the Church are on that account, null and void - but as quoted from Trent in bold above, this belief is condemned by Trent.
To all those marriage minded trads who may be probing those who've been married outside of the Church for potential candidates because they think those marriages are automatically all null, don't do it, they're not all null. The bottom line is that you're better off to consider that are all without any doubt valid, and continue looking for those never married. If they both said the words, "I do", then look elsewhere.