Marriage in Islam is essentially a social contract, and so long as it is contracted conforming to the stated requirements, it shall be deemed valid. The presence of an Imam at the function is not at all one of the stated requirements, but the marriage should be solemnized by someone who has been authorized to perform marriages.
The stated requirements of marriage in Islam are as follow: Full consent of both partners to the marriage, expressing the above consent through ijab (offer) and qabul (acceptance), finally the presence of two reliable witnesses. Apart from the above, in the case of females, their guardian’s consent has been considered essential for the validity of marriage according to the majority of imams and scholars. Imam Abu Hanifah, however, is of the view that a mature woman is fully capable of contracting her own marriage. Thus in his view, marriages finalized without guardian’s consent shall be considered as valid so long the woman has chosen someone who is considered as compatible. (ooh wow, I didn't know this previously)
Furthermore, scholars are also in general agreement to the fact that marriages should not remain a secret affair; rather they should be publicized. Another important integral of marriage is the bridal gift; although it is not essential to stipulate it in the marriage contract, nevertheless it must be paid either before consummation of marriage or after.
Now coming to the issue of contracting marriages in a society where Islamic laws are not enforced or recognized, it is also highly crucial to get the legal papers before marriage contract; for legal purposes, the marriage must be solemnized by someone who has been authorized by the law of the land to perform marriage. In the absence of such legalization, there is no guarantee of legal protection for anyone in the event of a dispute.
Although some people may consider legalization as being not so crucial, I would, however, insist that it is quite crucial and essential; it is not advisable for anyone to get married without legal papers. This fact can be emphasized by referring to the fact that marriage is primarily a social contract and as such we should do so in conformity with the laws of the land we live so that such a contract can be legally enforced.
Apart from this, Islam teaches us to do what we do as efficiently, methodically and professionally as we can. The Prophet (peace and blessings be upon him) said, “Allah loves you to do your work as best as you can.”
In conclusion, you should insist on getting the marriage done by obtaining the legal papers, and getting it solemnized by an Imam or a person who has been authorized to do so. So long as the marriage is done by fulfilling the above requirements, it shall be considered as valid. All other things such as arranging a grand wedding or throwing a big feast, etc. are all non-essentials as far as the validity of the marriage is concerned.
May Allah guide our steps in all our affairs and help us to remain steadfast on what is true and right, Ameen!
