Is it mandatory for a Roman Catholic girl to convert to Syrian Orthodox if the boy is of the Syrian Orthodox church, in the case of marriage?

The Malankara Orthodox Syrian Church is a break-away part of the universal Catholic Church and was formed after the Coonan Cross Oath , taken on 3 January 1653. It was a public avowal by members of the Saint Thomas Christian community of Kerala, India that they would not submit to Portuguese dominance in ecclesiastical and secular life. The swearing of the oath was a major event in the history of the Saint Thomas Christian community and marked a major turning point in its relations with the Portuguese colonial forces. The oath resulted in the breaking up of 54 years of Portuguese Padroado (Patronage) Jurisdiction over the Malankara Syrian Church, started with the synod of Diamper in 1599 A.D. convoked by the Portuguese Archbishop Dom Alexio De Menezes. While it is true that Malankara Orthodox Syrian Church does not accept the supremacy of the Pope, there are many common practices among the Roman Syrian Catholic Church of Kerala and the Malankara Orthodox Syrian Church. In fact, there is a rite in the Roman Catholic Church of Kerala called the Malankara Catholic rite (of members who had 'returned' from the Orthodox Syrian Church) which accepts the supremacy of the Pope and freely enter into matrimonial relationship with the Roman Syrian Catholics.

Reverting to the question, the Roman Catholic Church of Kerala has been permitting its members to enter into matrimonial relationship with a non-Roman Catholic believer provided that the member gives an undertaking that he/she will raise the children in Roman Catholic faith. Whether the Malankara Orthodox Church permits such marriages, can be answered better by its members. Hope someone is listening !

The Association of Interchurch Families, England, has published a copy of the following First Trilateral Agreement on Interchurch Marriages between the Catholic Church and the Malankara Syrian Orthodox Church (1994).

The Agreement states The Malankara Syrian Orthodox Church is an autonomous church under the authority of the Syrian Orthodox Patriarch of Antioch. It is thus one of those Eastern churches which the Roman Catholic Church recognises as close in faith to itself.

The Malankara Syrian Orthodox Church and the Catholic Church state they are agreed on the following considerations and norms (my emphasis):

Our two churches accept the sacredness and indissolubility of the sacramental bond of marriage and consider the conjugal relationship as an expression of the above communion and a means to achieve self­effacing mutual love and freedom from selfishness which was the cause of the fall of humanity.

In this theological perspective, taking into account the question of the marriages between the members of our two churches, we consider it a matter of our pastoral concern to provide the following directives.

Our two churches desire to foster marriages within the same ecclesial communion and consider this the norm. However, we have to accept the pastoral reality that interchurch marriages do take place. When such occasions arise, both churches should facilitate the celebration of the sacrament of matrimony in either church, allowing the bride/bridegroom the right and freedom to retain her/his own ecclesial communion, by providing necessary information and documents. On the occasion of these celebrations, the couple as well as their family members belonging to these two churches are allowed to participate in the Holy Eucharist in the church where the sacrament of matrimony is celebrated. We consider it also the great responsibility of the parents to pay special attention to impart to the extent possible and in mutual accord proper ecclesial formation to their children in full harmony with the tradition of the ecclesial communion to which they have to belong.

Outcome

According to this Agreement, the Roman Catholic bride can retain her Catholic faith and the couple can even participate jointly in the eucharistic celebration on special occasions when this joint celebration is socially required.

According to the Catholic Church's canon law on mixed marriages,

1983 Can. 1124 Without express permission of the competent authority, a marriage is prohibited between two baptized persons of whom one is baptized in the Catholic Church or received into it after baptism and the other of whom is enrolled in a Church or ecclesial community not in full communion with the Catholic Church.

The Syrian Orthodox are not in communion with the Catholic Church, since the latter considers them schismatic.

According to the Syrian's norms,

The liturgical minister should be the parish priest of the church where the marriage is celebrated, or his delegate from the same ecclesial communion.

and

There is to be no joint celebration of marriage by the ministers of both Churches.

and

Syrian Orthodox partner is to be reminded that he or she has to commit him/herself to imparting to their children proper Orthodox formation, to the extent possible and in agreement with his/her partner.

According to Catholic canon law, the first two points are possible, provided it is a Catholic priest and Catholic church. The last point is even more explicitly rejected in the older, 1917 formulation of Can. 1124 cited above:

1917 Can. 1060 Most severely does the Church prohibit everywhere that marriage be entered into by two baptized persons, one of whom is Catholic, and the other belonging to a heretical or schismatic sect; indeed, if there is a danger of perversion to the Catholic spouse and children, that marriage is forbidden even by divine law.

Also, regarding baptism, the Catholic Church requires that

Can. 868 §1. … 2/ there must be a founded hope that the infant will be brought up in the Catholic religion…

Thus, although certain things may be permissible on the side of the Syrians, the Catholic Church is very cautious regarding mixed marriages, as they can be very spiritually dangerous to all those involved.