Two Bahá’ís, when getting married, cannot have the religious ceremony of another Faith.

In reply to your letter of January 26th, we feel that while it is important to be flexible in requesting new believers, particularly youth who may encounter parental opposition, to withdraw from membership of other religious organizations, such flexibility cannot be allowed to extend to compromising Bahá’í law. Two Bahá’ís, when getting married, cannot have the religious ceremony of another Faith.

(Universal House of Justice, Lights of Guidance, p. 161)