The Pope is not "changing doctrine"Well, if you believe the press today you would think that the Vatican is about to change Church teaching on whether or not married couples can use condoms. The Pope is not changing Church teaching, nor is he about to. The Holy Father has ordered a study about whether or not the use of condoms by married people is medically effective in reducing the spread of AIDS, because AIDS is a particular problem in heavily Catholic sub-Saharan Africa. If the Pope were to decree that married people with AIDS may make use of a condom, he would be expanding on a doctrinal understanding that already exists within the Church.
In his 1968 Encyclical Humanae Vitae, Pope Paul VI explained the doctrine and dogma of the Church that the primary purpose of married love was the procreation of the human family. Hence, explained the Holy Father, the use of artificial means of birth control for the purpose of preventing pregnancy according to the plan of God while continuing to engage in sexual relations is sinful, because human beings have utterly no right to interfere in God's ability or will to create new life. It was understood, however, that the hormones in the birth control pill could be useful for other medical purposes, including regulating a woman's cycle to assist her in fertility. These medical purposes are not inherently sinful, and if those hormones are being used in these unsinful ways, then the use of "the pill" for these other medicinal purposes is not sinful. The key is whether the intended use is to prevent having a child, or to assist with some other medical condition in which the hormones might be of use.
If Benedict were to say that the use of condoms BY MARRIED PERSONS WITH AIDS is permissable to PREVENT THE SPREAD OF AIDS, that means that the Pope is allowing for a medical use because of necessity. If the Pope said this were permissable, it would be under the same conditions that the "pill" might be allowed namely:
A.) The intended use is as a result of a medical condition not related to the process of childbearing and
B.) The intended use has nothing to do with the prevention of pregnancy, but to prevent or cure some other health problem (in this case, to prevent the spread of AIDS)
C.) The persons utilizing that method of preventing AIDS would be doing so within the context of married life.
That is an expansion of an already existing understanding, not a change in doctrine, as the press would have us all believe. If I were the media, I wouldn't hold my breath. All the Pope has done is order a study, not make a final decision. Popes have a habit of "ordering studies" and then using it as a chance to shoot down whatever liberal notion it was that has been studied in Mount Sinai-esque fashion.
The long and the short: When you hear the press talking about "the Pope is changing such and such" consult a real Catholic to see what the truth is behind what the media is saying.