Q: Rabbi, is it possible to use the One Ring, to rule them all, in the ceremony of kiddushin to solemnize a marriage?
A: A good question, my child. The One Ring, which is said to have great powers in binding its wearer in the darkness (of a wedding bed?), might seem to be an excellent choice to bind two people together in marriage. We will consider the legal ramifications of this choice.
As you know, there are many rules and traditions on the matter of what gift a chosson may give to his kallah during the wedding ceremony, in order to acquire her as his bride. First, it must be worth at least a perutah; that is, a coin sufficient to purchase the smallest item that may be purchased alone. In one known case, a wedding ceremony was invalidated due to the supposed groom giving a bottle cap to his purported bride, when a bottle cap is not, in fact, worth a perutah.
It would seem that the One Ring is indeed worth more than a perutah, as it is of such great value that lords of Men and Orcs all over Middle-Earth consider it priceless. It is made all of gold, as is our tradition for wedding rings. We do not use gems in wedding rings, as the gems could conceivably be false, and then the value of the betrothal would be unknown. Thus we learn that it is not permissible to marry using the Three Rings of the Elves, the Seven Rings of the Dwarves, or the Nine Rings given to Men, all of which include stones.
However, the reason we give wedding rings made only of pure metal is that these rings may be melted down, and the value of the gold weighed. It is known that when the One Ring is tossed into a fire, it does not melt; instead it reveals words of flame. The One Ring may not be true gold according to halacha, and therefore its value may not be tested. Furthermore, at no point in the Third Age has the One Ring been sold for purchase; we do not know what value in coin could buy it. The One Ring may not in fact be worth a perutah.
There are, of course, other requirements for a true marriage. The gift must also be delivered with intent to marry; that is, the chosson must utter the words Harei at m'kudeshet li k'daat Gandalf v'Eretz haTichonah, "You are sanctified to me according to the laws of Gandalf and Middle-Earth," at the time he delivers the gift. In general, the person giving the One Ring to another party tends not to remember to utter these words; he is more likely to say, "My precious! You've stolen my precious!" From this we learn that Bilbo Baggins is not actually married to Gollum, despite the passing of the Ring, nor has Bilbo Baggins wedded Frodo Baggins. A chosson with the strength of will to remember the kiddushin formula at the moment he surrenders the One Ring would be a fine husband indeed.
There is the small dilemma that the One Ring twists all vows sworn upon it to evil. There is also the further dilemma that one would hardly want to have a wedding ring that renders the wearer invisible. Tsnius is a great virtue, of course, but this is ridiculous.
For all of these reasons, this teshuvah rules that it is not permissible to use the One Ring in kiddushin. Try something a little less cursed, like the Ring of the Nibelung.