Single people fornicate. Married people commit adultery.
I believe this is the annulment clause. If spouses are fornicating then it is not a valid sacramental marriage.
If one or both of the spouses were fornicating with others at the time of the marriage then it can be evidence of a non-sacramental union because it shows that they never intended to have unity within the marriage alone.
Would you share where this info came from? I've not heard of fornication making a marriage invalid.
Code of Canon Law:
Can. 1101 §1 The internal consent of the mind is presumed to conform to the words or the signs used in the celebration of a marriage.
§2 If, however, either or both of the parties should by a positive act of will exclude marriage itself or any essential element of marriage or any essential property, such party contracts invalidly.
Can. 1056 The essential properties of marriage are unity and indissolubility, which in Christian marriage obtain a special firmness by reason of the sacrament.
Is this Code of Canon Law the 1983 version?
That was the 1983. And here are the same statements from other sources:
1917 Code Canon 1013 - §2.
The essential properties of marriage are
unity and indissolubility, which acquire a special firmness in Christian marriage by reason of its sacramental character.
Council of Trent:
Definition of Matrimony
Matrimony, according to the general opinion of theologians, is defined: The conjugal union of man and woman, contracted between two qualified persons, which obliges them to live together throughout life.
In order that the different parts of this definition may be better understood, it should be taught that, although a perfect marriage has all the following conditions, - namely, internal consent, external compact expressed by words, the obligation and tie which arise from the contract, and the marriage debt by which it is consummated; yet the obligation and tie expressed by the word union alone have the force and nature of marriage.