Right, but the thing is even if they don’t know that they’re Catholic they are still bound. Imagine I was baptized Catholic as a baby. My parents never took me back to the church. I was provided with no religious education. As an adult, I had a conversion experience and joined a protestant church. I get married in the protestant church. I’m now objectively fornicating, living in an objectively invalid marriage… and I have no clue and never will… that doesn’t seem fair or just. And no, it’s not a matter of divine law… it’s a matter of Church law. The Council of Trent bound Catholics to marry in the Church… prior to Trent, Catholics could validly, though illicitly, marry in a civil ceremony. The Church could change this requirement tomorrow… it would still be illicit to marry outside of the Church, but at least these couples wouldn’t be living in a perpetual state of fornication… it seems to me it would be an act of mercy.