 The church will then make a determination that the marriage was invalid from the beginning, and there was some defect present, which meant that there was a nullity here. It was not a valid marriage from the beginning, and then they will issue that decree that says you are free to remarry. But just because you got a divorce, you are still married in the eyes of the church. And so to marry after the divorce without an annulment is where the sin comes in.