I'm unfamiliar with this. Can you elaborate?
A finding of nullity is a judgment of a chuch court (tribunal) which, after reviewing evidence and testimony, conludes that there was some severe defect in the marriage vows from the git-go.
A defective vow isn't a vow; and without authentic vows there cannot be a binding sacramental marriage.
If one of the parties to the vows was drunk, on drugs, underage, mentally defective, under threat or duress (gun to their head), ineligible to marry (because of blood relationship or because of being already married to somebody else, for instance), knowingly lying to or deceiving the other party --- for any such reasons or similar, the tribunal finds that the marriage was never sacramental, because the vow was a "nullity."
This has no impact whatsoever on civil marriage or on the civil legal status of the would-be spouses or their children.
What it does have impact on, is the canonicity of the original marriage. By bringing objective evidence and standards to bear on the validity of a marriage, it should be an aid to the examination of conscience. If the parties have a conscience.
May God help these wretched people.
In order for a Sacrament to be VALID, both parties have to be free to make the promise, that is, they cannot be legally married to anyone else, and must agree to certain commitments; be faithful to each other in the marriage, and be willing to accept children from God, and raise them in the Faith.
If either party lies about their willingness to do that, or demonstrates that unwillingness during the marriage, there is likely evidence to affect an annulment of the Sacrament. This only occurs after a Marriage Tribunal has investigated both parties, has taken testimony from both sides, and has given the matter much thought and prayer. This is also completely separate from any legal actions in the civil courts.