The people involved can have as much certitude as they want. I know I’m married. I don’t “presume” I’m married: the legal system presumes it, not me.
Just to play devil’s advocate, can a person involved really have 100% certitude? Who is the arbiter of validity? An individual’s level of certitude, or the Tribunal’s judgment?
I would submit that an individual’s level of certitude concerning marital validity is, by definition, that individual’s personal assessment of whether he or she believes the legal system’s presumption of validity can be rebutted. And if that assessment depends on facts that an individual
cannot know with 100% certitude - interior dispositions of his or her spouse - he or she cannot have 100% certainty.
For example: Husband, like you,
knows he is married. The legal system, as you note,
presumes it. With “full favor of the law.”
Unbeknownst to husband, wife has never wanted children. She has always felt this way, she expressed that to several credible witnesses prior to and following the marriage, and has been secretly using contraception for the duration of the relationship. All without husband’s knowledge.
50 years later, the childless couple divorces. Wife petitions the Tribunal for a decree of nullity. Husband opposes the petition. He knows he is married. 100% certain. Is he right?
This is how it has to be. OP may not like it. And, the odds of the example above are hopefully incredibly low. Can we not just admit it though?