I am not versed in Cannon law either, but I have a couple of questions for you.
1) Presuming the natural method of coitus with your spouse, with or without fertility drugs, does not work, why would a couple not adopt rather than use the extreme meaures of in-vitro fertilization, surrogate motherhood, etc?
2) If a regular result of the extreme measures is fertilized ova that are frozen forever, discarded, or harvested for stem cells, would that impact your position on these measures?
3) If the problem is that the woman's uterus just won't hold an implated egg, how many of these ova (babies) would they use (kill) in trying to get it to work before giving up?
These are honest ethical questions, not challenges or attacks. The first one came up when a caller was asking Dr. Laura about a child she was carrying as a surrogate for her sister. The caller was asking Dr. Laura what she should tell her own child about the baby she would deliver that would not be hers. Dr. Laura asked why her sister didn't just adopt. Was it ego that decided they must use whatever means necessary to keep their own genes in the pool? On the other hand, Levitical law commands a man to impregnate his brother's widow if she is childless so the line may be carried on so it is a real question.
Shalom.