22:23 Jul 8, 2011 

of Flemish legal text and I haven't seen anything like this. But I think that it just refers to their capacity to get married, i.e. there being no impediment.
Thinking about this, actually it may just be a declaration you make at 6 weeks before you want to get married in the town hall and maximum 6 months. After approval (when they have checked up on you) that you may book a date (if I remember well). Come to think of it they do ask you when you file an application whether there should be an impediment.
The capacity, though, may also refer to the fact that both parties are of age and can act by themselves instead of needing a guardian to do so. That is also established in your application.
Context can maybe bring solace.

22:01 Jul 8, 2011 

The wording seems to be Flemish. 'De twee partijen spraken hun capaciteit om the handelen uit' probably suggests 'they stated that they have competence to act/are capable of contracting.

The lack of logic is found in that they wish to be married after they declared that there is no impediment to preventing them to be married. In other words: Yes, we want to be married but please stop us to do so!