What if you’re an atheist as is your spouse, you’ve always wanted a normal marriage with children, permanence and no cheating, didn’t exclude anything important, were both mature enough and understood what you were doing? Would that marriage not be valid? Why?
Or what authority does a Protestant minister have? He’s a layman like you or I unless he actually has valid orders for whatever bizarre reason, but even then, he’s not acting in any ordained capacity. Or a non-Christian cleric. Or a priest of one of a million gods in a politheistic religion. What difference does it make?
Even in the Catholic Church, a layman can be designated to assist at marriages, by the way. In times up to middle ages, the Church didn’t require a religious celebration at all. Divorce was forbidden, some people were off limits and that was it.
@dulcissima: Yes, although sometimes civil authorities will prescribe some conditions for validity of marriage. Then they could say if you didn’t have domicile, your marriage was invalid. Or if the judge was an impostor, then you didn’t marry. Or you had incurred some penalty legally preventing you from marrying anyone. That wouldn’t apply to validity of marriage as seen by the Catholic Church.