We know that ideal, by-the-book situations are far less common than not. The Church recognizes this, and affirms the potential when pastors meet engaged persons where they are.
20. In conducting the preparation, pastors, taking into account prevailing attitudes toward marriage and the family, should endeavor to evangelize the couple’s authentic and mutual love in the light of faith. Even the requirements of law for contracting a valid and licit Marriage can serve to promote a living faith and fruitful love between the couple, ordered toward establishing a Christian family.
Pastors are obliged to make “every effort.” That cannot be understated.
21. But if every effort fails, and an engaged couple openly and expressly demonstrate that they reject what the Church intends when the Marriage of baptized persons is celebrated, the pastor of souls is not permitted to celebrate the Sacrament. Though reluctant, he must take note of the situation and convince those involved that, in these circumstances, it is not the Church, but they themselves, who prevent the celebration they are asking for.(Familiaris Consortio 68)
This only has a hope of ringing true if “every effort” is made.
The text cited in blue is from the English translation of The Order of Celebrating Matrimony © 2013, International Commission on English in the Liturgy Corporation. All rights reserved.