[WriteOn]

That is the law. but many things have been canon law. It changes slowly, but it changes.

[Mrs. Don-o]

Some parts of Canon Law are "positive" law (it's the law because we wrote it that way: analogous to in the US everyone drives on the right, but in the UK on the left); other parts of Canon Law are based on truth, i.e. dogma (profaning the Eucharist isn't a sin just because it's against Canon Law; it's against Canon Law because it's a sin.)

The Church's default position is that a marriage vow is valid and binding unless proven in a court of law to have been defective ; that refers to a constitutive element of a sacrament --- Marriage vows are binding, as Jesus Himself taught --- therefore the Church always has to presume the vows are binding unless proven therwise.

Now, the grounds for Annulment may vary. That's the part that can change --- within limits.

For instance, right up until almost the modern period, marriages were arranged by parents, and children could be betrothed (promised) in marriage even as minors. That was never grounds for an annulment. It would be now, though, since psychological maturity is much more emphasized as determining the validity of a vow.