All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad (saw) is His Slave and Messenger.Having witnesses is a condition for the validity of the marriage, and it is also a condition that the two witnesses be Muslims. The testimony of a non-Muslim is not valid for the marriage of a Muslim.Therefore, if the marriage contract was concluded with two or more Muslim men as witnesses, then it is a valid marriage (even it is not registered nor signed).As regards registering the marriage on paper, then this is for additional confirmation and it does not affect the validity of the marriage. If this document is signed by a non-Muslim, it does not affect the validity of the marriage.For more benefit, please refer to Fatwa 224146.Allaah Knows best.
(Source: islam_web) Classified in Women and Family > Marriage Contract