Gestational surrogacy is the arrangement by which a couple arrange to fertilize the woman's egg with the man's sperm, then have the fertilized ovum implanted and gestated in another woman's womb. In the U.S. the practice is regulated by state law, illegal in some states, legal in others, which means that in practice it is legal, since the couple can arrange to do it in a state where it is legal.
I gather, however, from a conversation with someone who has been researching the subject, that in most of western Europe it is illegal, and that while it is legal de jure to arrange to have it done abroad—India and the Ukraine are apparently the favored destinations—it is made difficult de facto by administrative obstacles put in the way of bringing the resulting infant back to its parents' home country. The U.K. is a partial exception; gestational surrogacy is legal, but only if it is altruistic, which is to say, only if the host mother is not paid for undergoing the inconvenience and risk of bearing another woman's child.
Which raises an obvious question: Why would anyone be against the arrangement? In many cases, it makes it possible for a couple to have a child—their own child—when they otherwise could not. Even in those cases where the biological mother could bear her own child, why should anyone else object if she can find another woman willing to do it for her on mutually acceptable terms?
There are, I think, a number of possible answers, although none that in my view justify the restrictions. One is that the decision to be a host mother is not freely made since it is "compelled" by poverty. This sort of argument is common in a variety of contexts, but I find it hard to make any sense of it. Put in its simplest terms, the claim is that if the potential host mother does not accept the offer she will starve to death, hence accepting the offer is not really a free choice, hence she should not be permitted to make it. Which, if the starting point is correct, means that out of our generous concern for a poor woman we will compel her to starve to death.
A second possibility, following a line of argument originated (I think) in the context of prostitution by professor Margaret Radin of Stanford Law School, is that by permitting a woman to rent out the use of her womb (body) we "commodify" motherhood (sex), cause people to think of it as something to be bought and sold, and so cheapen the human experience. Restated, the claim is that the transaction of buying sex or renting a womb is both an exchange and a statement. The exchange is one that, in Radin's view, should be permitted, since the woman owns her own body and so is entitled to decide how it is employed. But the statement, because of its effect on other people's view of their lives, is one that ought not to be made, hence the transaction may, arguably should, be prohibited.
What is bizarre about this argument is that it was made by an American law professor. The American constitution, as routinely interpreted by judges and law professors, contains a very strong protection for freedom of speech, making it a violation of the constitution to prohibit an act, such as flag burning, which is also speech. Following out that principle, Radin's argument ought to imply that even if there were good reasons to prohibit surrogacy or prostitution, the fact that both are speech as well as acts ought to protect them. She, along with those who accept her argument, reaches precisely the opposite conclusion.
A somewhat better argument that might be made against surrogacy is that permitting a couple to produce a child when they otherwise could not means that they will have no need to adopt, hence prohibiting surrogacy benefits children in need of parents. There is some logic to the argument, but its morality is questionable. Surely a legislator willing to forbid a couple from producing their own child in the only way they can in order that they will have to adopt someone else's ought at least to feel obligated to refrain from producing any children of his own until he has adopted at least one.
Finally there comes what I suspect is the real reason. Natural is good, and surrogacy (like IVF before it, and many other things as well) is unnatural. Our grandparents didn't do it, our pre-human ancestors didn't do it, so there must be something wrong with it, something wicked, sinful. Icky.
And worse still if done for money.
On the principle of full disclosure, I should mention that my granddaughter Iselle might not have come into existence were it not for surrogacy. A hard argument to rebut (see below).