God made certain immutable laws (from our perspective) called, in toto, the Divine Law. These are usually given through revelation – principally, from Scripture. He also created Nature according to those laws so that the so-called Natural Law is a manifestation of the Divine Will (Law), but only a subset of it, since Natural Law is finite and Divine Law is, essentially, simple, infinite, and eternal.
Man, being made in the Imago Dei with free will is endowed, in a like manner, to construct or “posit” laws to govern the Earth and all therein that he was given to “subdue.” It is understood that these so-called positive laws (posit -ive) are subsets of both the Divine and Natural Law and derive their rights as laws from them. To the extent that a positive law contradicts either Divine or Natural Law, it ceases to have any force as law, just as a contradiction in a mathematics proof invalidates its right to be called a proof.
In Divine Law, marriage implies a definite ontological change of two flesh (a man and a woman) becoming one by following a certain prescribed process (a teleology). Once this ontological change happens, it can’t be undone except by an act of God who ends the union at death. All valid derivative positive laws of man relating to marriage must start from that ontological reality or they fail, by virtue of being inconsistent with Divine Law, to be really and truly accorded the status of a law. Real, consistent, positive laws that are in accord with Divine Law give specific real rights; disordered and inconsistent acts of the imposition of power rather than authority over another that one simple chooses to call, ipse dicit, a law, do not confer real rights, because they are not, in reality, laws. Behind every valid right, there is a valid law, so the process is symmetric under implication (i.e., biconditional: laws imply rights; rights imply laws).
The so-called, “Equal Marriage Rights,” idea, however, implies that a law must exist behind it permitting same-sex “unions” to be equated, somehow to marriage and this is a direct contradiction to Divine Law, since marriage has a specific definition outside the power of Man to change or to make equal to it something else. Thus, any “law,” equating same-sex unions to marriage is invalidated from the start and cannot ever, properly, be referred to as a law, nor recognized as such except by the insane – since people who seek unnatural power over others are either following a distortion of reality that puts THEM at the center of the universe (make no mistake – behind every argument for same-sex marriage there is someone with a God complex) or they cannot recognize reality to begin with. Man cannot give what he does not have. To give equal status to same-sex civil unions as any other natural union would give man a power reserved to God.
Now, some people simply do not believe in God. They believe, as Hobbs does, that all laws start with Man. Of course, even Hobbs did not believe that you could pass a law saying that, “henceforth, all circles shall be squares,” – but that is exactly what the same-sex laws are trying to do. Divine Law and Natural Law both invalidate a positive law allowing same-sex unions. In fact, these “laws” are so abhorrent that, in my opinion, they may be resisted by violence, if need be (that will some day come to pass, but not yet). Certainly, they can never, except by the morally insane, be mentioned in the same breath as real and true laws.
So, in the case of same-sex permissive, “laws,” we are left not with authority, from which all laws properly flow, but, rather, blind, naked, power. Rather than creating peace, it creates chaos. Such laws are a form of abuse. The CCC says:
1902 Authority does not derive its moral legitimacy from itself. It must not behave in a despotic manner, but must act for the common good as a “moral force based on freedom and a sense of responsibility”:21
A human law has the character of law to the extent that it accords with right reason, and thus derives from the eternal law. Insofar as it falls short of right reason it is said to be an unjust law, and thus has not so much the nature of law as of a kind of violence.22
1903 Authority is exercised legitimately only when it seeks the common good of the group concerned and if it employs morally licit means to attain it. If rulers were to enact unjust laws or take measures contrary to the moral order, such arrangements would not be binding in conscience. In such a case, “authority breaks down completely and results in shameful abuse.”23
As to the Church using equivocal definitions of marriage – that simply is not true. The Natural, Canonical, and Sacramental aspects of marriages are all nested within the one true ontological and unequivocal definition of marriage. This is true even in the Old Testament, except when God chooses to temporarily suspend the definition – and, He, being the author of the Law, is the only one who has that right.
Related link: The Chicken's Comment on WDTPRS