Non-Muslim nikah at the Masjid.Can Imam Perform a nikah between Non-Muslims without them accepting Islam. What is the ruling of such Nikah, knowingly after such nikah they will proceed in their kufr.Question two.What is the ruling of two muslims marries in the church, proclaiming in the name of jesus. after doing is lamic nikah at the masjid. is their islamic nikah still stand?

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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is impermissible for a Muslim to conduct the marriage of a non-Muslim couple. A Muslim cannot act as a Wali (legal guardian) in the marriage contract of a non-Muslim bride. Difference of religion precludes someone from being a Wali in marriage according to the consensus of Muslim scholars. Ibn Qudaamah said: "As for the Muslim, he cannot act as a Wali for a non-Muslim bride except in the case of a master-slave situation or a Muslim ruler and a non-Muslim woman living in the Muslim state (Thimmi citizen), because Allaah The Exalted says (what means): {And those who disbelieved are allies of one another.} [Quran 8:73] Moreover, difference in religion is among the impediments of inheritance; a non-Muslim is not entitled to inherit from a Muslim relative and vice versa. The same applies to the laws pertaining to blood money concerning killing; a Muslim relative is not obliged to pay the Diyah (blood money) on behalf of a non-Muslim relative and vice versa." [Al-Mughni]

The jurists held different opinions about whether or not it is permissible for non-Muslims to enter the mosque; the most valid opinion in this regard is that it is permissible in the event of a guaranteed benefit, such as them being encouraged to embrace Islam and the like.

As for the second question: it is impermissible for Muslims to conduct their marriage in a church because it involves contraventions of the Islamic Sharee‘ah, some of which were highlighted in Fataawa 87484 and 91215.

The expression mentioned in the question, "proclaiming the name of Jesus", is ambiguous and requires clarification on your part. If you mean that those Muslims made mention of Jesus in a manner that involves disbelief, as in the Christian ritual words "In the name of the Father, and of the Son, and of the Holy Spirit", then this entails apostasy and takes the doer out of the fold of Islam, and it entails the annulment of the marriage as well. It is incumbent on Muslims to be mindful of such evil and beware of it. Also, Muslims are enjoined to display commendable pride in their religion, adhere to the Islamic teachings and avoid imitating non-Muslims.

Allaah Knows best.