This is a list of the five non-negotiable issues of the Catholic Church
The Church teaches that, regarding a law permitting abortions, it is "never licit to obey it, or to take part in a propaganda campaign in favor of such a law, or to vote for it". Abortion is the intentional and direct killing of an innocent human being, and therefore it is a form of homicide. The unborn child is always an innocent party, and no law may permit the taking of his life. Even when a child is conceived through rape or incest, the fault is not the child's, who should not suffer death for others' sins. Another sub-set issue within this subject area that is non-negotiable pertains to Human Reproductive Technologies, which includes the Church’s position against Contraception, In-Vitro Fertilization and Sterilization.
Often disguised by the name "mercy killing;' euthanasia is also a form of homicide. No person has a right to take his own life, and no one has the right to take the life of any innocent person. In euthanasia, the ill or elderly are killed, by action or omission, out of a misplaced sense of compassion, but true compassion cannot include intentionally doing something intrinsically evil to another person.
3. Embryonic Stem Cell Research
Human embryos are human beings. "Respect for the dignity of the human being excludes all experimental manipulation or exploitation of the human embryo". Recent scientific advances show that medical treatments that researchers hope to develop from experimentation on embryonic stem cells can often be developed by using adult stem cells instead. Adult stem cells can be obtained without doing harm to the adults from whom they come. Thus there is no valid medical argument in favor of using embryonic stem cells. And even if there were benefits to be had from such experiments, they would not justify destroying innocent embryonic humans.
4. Human Cloning
"Attempts ... for obtaining a human being without any connection with sexuality through ‘twin fission,’ cloning, or parthenogenesis are to be considered contrary to the moral law, since they are in opposition to the dignity both of human procreation and of the conjugal union" (RHL 1:6). Human cloning also involves abortion because the "rejected" or "unsuccessful" embryonic clones are destroyed, yet each clone is a human being.
5. Homosexual "Marriage"
True marriage is the union of one man and one woman. Legal recognition of any other union as "marriage" undermines true marriage, and legal recognition of homosexual unions actually does homosexual persons a disfavor by encouraging them to persist in what is an objectively immoral arrangement. "When legislation in favor of the recognition of homosexual unions is proposed for the first time in a legislative assembly, the Catholic lawmaker has a moral duty to express his opposition clearly and publicly and to vote against it. To vote in favor of a law so harmful to the common good is gravely immoral".