1-A marriage between a man and woman in a religious ceremony. For discussion sake, the marriage is valid.
Well yes, of course. Having said that, the Church allows the parties in a valid marriage to be dissolved in civil court and their belongings divided, when a grave reason exists. If you are validly married to a woman who chooses to abuse or abandon you or a man who later chooses to gamble away your life savings, you are morally allowed to obtain a legal separation, annulment, or even a divorce, if it is required for reasons of justice, safety from harm, etc. In that case, there is no marital debt with regards to physical relations. You are only bound to live as one not free to marry; that is, in a celibate manner.
2-A marriage between a man and woman in a religious ceremony. For discussion sake, the marriage is invalid.
While the marriage is putatively valid–that is, before it is found and declared defective–there is no sin if the parties, in good faith, treat the putative marriage as valid. Any children born of the putative marriage are considered to be the product of legitimate marital relations.
The Church does not even use the concept of “illegitimate children” any more, but some families who go through divorce and subsequent annulment understandably find the concept of the legtimacy of honoring the attempt at marriage very important, for obvious reasons. Assuming good faith, there is no retroactive immorality in a marriage later declared null.
3-A marriage between a man and woman in a civil ceremony. For discussion sake, the marriage is valid.
The marriage contract is real and must be honored morally. Spousal relations, if they do not include a Catholic (whose marriage is not complete until it enjoys canonical form) are legitimate. Unlike a sacramental marriage, though, such a marriage may legitimately be dissolved later, under the right conditions (under the Pauline or Petrine privelege, for example.)
4-A marriage between a man and woman in a civil ceremony. For discussion sake, the marriage is invalid.
The parties are not free to marry and must act in a celibate manner until a civil divorce or annulment is obtained. My understanding is that if the only defect in the marriage is a defect in form, valid consent lacking canonical form is ratified retroactively by the Church upon convalidation. Nevertheless, a couple that includes a Catholic that is aware that their marriage is not yet valid are bound to abstain from marital relations until the process of marriage is completed, even if their marital consent has no other defect.
5-A marriage between two men or between two women in a religious ceremony. This is obviously an invalid “marriage.” However, is there a spousal relationship? For example, would a man commit adultery against his “husband” if he dated a woman while he was “married.”?
6-A marriage between two men or between two women in a civil ceremony. Same comments as no. 5.
Well, obviously the religious ceremony isn’t Catholic and violates the Catholic understanding of valid matter for marriage of any kind. The consent is not elevated beyond the consent given between two friends anywhere else outside the Church. To the degree that the consent is morally repugnant, the parties are each morally bound to repudiate the consent, whether or not the other party does. In fact, if the religious ceremony has no standing in civil law, it is actually less morally-binding than a civil ceremony would be.
A person who has legally contracted such a union must meet the requirements that allow a marriage under civil law before he or she can contract a marriage in the Church. The union must be dissolved under civil law before the person could marry in the Church. A Catholic must not give the appearance of having committed bigamy, but also may not violate civil law any more than divine law dictates that he or she must.
While they are not spouses, their promise may truly be one of friendship, as well. Homosexuals are bound to treat each other with the respect due to every human person, as much as anyone else is. To the degree that the relationship includes some virtue, it is binding in those terms, even though strictly only under those terms, and strictly under the moral compulsion to avoid future near occasions of sin. Even though the romantic relationship itself is morally repugnant, there can theoretically be understandings that are morally binding to the degree that the friendship is moral. In other words, the repugnant nature of the consent still does not free anyone to be a jerk, to be greedy, unkind, rude, to evade any legitimate duty to perform spiritual or corporal works of mercy, or any of that. The necessity to avoid near occasion of sin and to avoid giving public scandal has to be honored, though.
When one of the pair leaves the relationship or the couple dissolves it, as moral law dictates must happen, he or she is ethically bound to say so up front, provided there isn’t legitimate fear of reprisal to consider. When the separation occurs, the two are bound to be just in dividing their belongings, they are still bound to be charitable to each other, that kind of thing. They are also bound to follow the civil law with regards to any legal contract they set up, excepting where it violates divine law. But no, there is no marriage, no right to “consort”, none of that, no matter what the state calls it, because that violates divine law.
Also, if a domestic partnership law were to be on the books that clearly DOES NOT imply a spousal relationship, a Catholic could morally enter into it. In other words, if civil law were to allow single adults to enter into relationships that were theoretically the equivalent of a two-person monastery, so that there is no public scandal, then a pair of same-sex Catholics could use that law for the financial or other legal advantages it legitimately offers.