Question: A sister has completed a Legislated marriage contract. Now she wants to complete a civil marriage in a disbelieving country in order that it be known that they [the couple] are married and for administrative records, knowing that the one who will marry them is an administrator who is a disbeliever. They require witnesses for this contract. Is it allowed for me to be a witness for her?
Answer: “There is no preventative in regards to it. As long as they agreed to this and they are not capable of Hijrah and they cannot remain except through this [contract], and they are not capable of announcing the marriage except through this [contract]. As long as they have completed a Legislated marriage contract which is valid, then they want to complete a civil marriage in order to obtain [the status of being married]”
[https://www.alnajmi.net/voices-action-show-id-1421.htm]
Translated by
Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan