In the present situation it's highly debatable just who could make a binding decision regarding nullity. Marriage law itself is large and complex (here's the canons regarding marriage from CIC1917, with commentary, over 400 pages https://archive.org/details/1917CodeOfCanonLawCommentary/page/1/mode/1up).
I think, at the present time, unless it is a very clear-cut case, the safest course is to presume validity.
Thank you Emile. I looked up Canon 1098 in the commentary you linked here, and what it says about canon 1098
that Epiphany quoted is completely different from what he said.
Error is a state of mind in which one mistakes one thing or person for another, as for instance, when we think A is B or a crowbar is a poker. In the first-mentioned case we have what is called error about the person. Now since marriage is effected by the consent of the contracting parties, and the will can desire nothing except what is proposed to it by the intellect, it is evident that such a mistake affects the very substance of the matrimonial consent. Gratian sets forth the example of Lia and Rachel, but his solution is rather quaint. He could have simply answered that an error about the substance of the contract nullifies the consent. It would be an error about the person if James married Olga, when he intended to marry her sister Gemma. Such errors are rare because it is seldom that two sisters resemble each other so closely that they can hardly be distinguished.
So an error about a person means thinking one person is someone else, not a quality about the person as Epiphany tried to argue. But in case it wasn't clear enough, this theologian explicitly lays this out:
Error about the qualities of the other party is of more frequent occurrence. However, here a distinction must be made. It may be that the quality concerning which one is in error affects the person merely in an accidental way. For instance, Joseph Buro, a citizen of Bruxelles, who went by the name of Buro de Chancartier, married a baroness of Leyden, by name of Theresa Kraus, a rich widow. She protested at the trial that she would never have married Buro had she known that he was not of the nobility. This was a purely accidental quality, and no error that reflected directly or indirectly on the person, and therefore the marriage was declared valid. From this is may be seen that a mistake about an accidental quality (wealth, intelligence, domestic habits, peaceful disposition, health, even concealed pregnancy by another man, etc.) does not alter the substance of the marriage-object, which is the person itself.
This should answer the questions that several other people have asked, about whether lies or concealment about adultery, pregnancy, drug addiction, or other major problems invalidates a marriage, and according to pre-Vatican 2 commentaries they do not. This is even a case of someone who lied in claiming to belong to the nobility in order to marry a rich noblewoman, and Rome said the marriage was valid, even though the noblewoman would never have married that man if she had known he was a commoner.