Living as we are in a period that exalts individual desires, especially regarding sexuality, many persons who consider themselves Catholics believe that they have a right to contract marriage in the Church in accordance with their own opinions on marriage. But really that is not the case. Baptized Catholics have the right to celebrate marriage in the Church only if they intend to contract marriage with the firm intention of fulfilling what the Church teaches about marriage. If persons request to be married, but reject or only partially accept the objective definition of marriage given by the natural law and the Church, they do not have a right to marry. Instead, what these persons are pretending to do is obtain the recognition of a non-existing right, or mint a new false right, as many persons and groups are currently doing. It is particularly important to understand that marriage is an objective reality, and that future spouses do not have a right to redefine its content. An attempt to redefine marriage will lead to its subversion, and even will open the door to polygamy, or worse, to same sex unions.
From both a natural law perspective and from the teachings of the Church, the spouses have a right to freely select the person whom they are going to marry, but they cannot negotiate the ends and properties of marriage. Marriage is a contract with regard to the selection of one’s spouse, but is not a contract with regards to its conditions. With regards to its conditions, those choosing to enter into marriage are free to enter or not enter into this state, but they are not free to change the ways in which it is regulated.
This was very clearly explained by Pope Benedict XVI in an important address that he delivered  in January of this year to the Tribunal of the Roman Rota. Given the importance of the message, it has received very limited publicity.
The Holy Father criticizes the fact it has been “often maintained that in admitting couples to marriage pastors must have a broad-minded approach, since people’s natural right to marry is at stake.” But what we must understand is that this right only exists when the future spouses are committed to celebrate their marriage in accordance with the Catholic definition of marriage.
The Holy Father stated in very precise terms that:
[The right to marry] is not a subjective claim that pastors must fulfill through a merely formal recognition independent of the effective content of the union. The right to contract marriage presupposes that the person can and intends to celebrate it truly, that is, in the truth of its essence as the Church teaches it. No one can claim the right to a nuptial ceremony. Indeed the ius connubii (the right to marriage) refers to the right to celebrate an authentic marriage. The ius connubii would not, therefore, be denied where it was evident that the fundamental requirements for its exercise were lacking, namely, if the required capacity for marriage were patently lacking or the person intended to choose something which was incompatible with the natural reality of marriage.
Thus, if the future spouses choose something that is not in accordance with marriage, pastors should refuse to celebrate the sacrament. Obviously this opens the question on how many Catholic pastors have the courage to refuse admission to marry to couples that do not have the right intent.
The only solution to this problem is serious marriage preparation, as the Holy Father reaffirmed in Sacramentum Caritatis , pastors should give:
maximum pastoral attention to training couples preparing for marriage and to ascertaining beforehand their convictions regarding the obligations required for the validity of the sacrament of Matrimony. Serious discernment in this matter will help to avoid situations where impulsive decisions or superficial reasons lead two young people to take on responsibilities that they are then incapable of honoring.
A proper preparation for marriage should not be seen by a persons planning to form a family as a limitation to their right to marriage, nor a burden. Totally to the contrary, it is their right to be assisted by the Church in the process of making this fundamental decision.
This careful preparation and serious verification of the intent of the future spouses should be an effective pastoral action, as the Holy Father underlines it:
It is necessary to make every effort to interrupt, as far as possible, the vicious circle that often exists between a predictable admission to marriage, without an adequate preparation and a serious examination of the prerequisites for its celebration, and a legal declaration sometimes equally facile but of a contrary nature, in which the marriage itself is considered null solely on the basis of the observation of its failure.
It is evident that the Holy Father has in mind the many couples who are admitted into the sacrament in easy or perhaps even in frivolous way that leads to invalid marriages.
Pastors have to be ready to uphold the basic teachings of the Church regarding marriage and family. As a consequence, they should not admit to the sacrament of marriage those who are not properly prepared or disposed, or those who dissent from Church teaching with regards to the ends and purposes of marriage. Pastors who take this role seriously may suffer persecution, and will likely be considered rigid and unbending; but their witness will be a form of martyrdom that will be prophetic in preserving the God’s plan for marriage and family.