Some declare that "you can't legislate morality." Let's look more closely at what that statement means.
If it means the law is not sufficient to make everyone morally responsible, that is certainly true. We need more than laws to make people good. Their hearts and minds need to be converted. Laws do have both a teaching and restraining function, however, that actually keep people within the bounds of moral behavior, even if unwillingly. As Rev. Dr. Martin Luther King, Jr. observed, the law can't make my brother love me, but it can keep him from lynching me.
If the phrase means the law is not the source of morality, that is also true. Morality comes not from law, but from the nature of the human person, which ultimately flows from the nature of God.
If the phrase means laws have nothing to do with morality, as if there is a total separation between one's "moral life" and one's "social life," this is patently false. This is the idea that whatever a law says is OK is OK. In reality, however, majorities can be wrong. Furthermore, both morality and law deal with human behavior. Any time you legislate the boundaries of human behavior, you are legislating morality.
It seems that the "you can't legislate morality" argument arises most often when the Church speaks up for the right to life of every human person, from conception to natural death, and when the Church insists that such a right must be protected by law. The US bishops did this quite eloquently in their document Living the Gospel of Life: A Challenge to American Catholics (1998). Commenting on the criticism that often follows such assertions, Cardinal John O'Connor once wrote, "Why are bishops criticized only when the public policy question involves abortion? Why would I be praised for encouraging the mayor, the governor, the Congress and the president to intensify the war on drugs, but criticized if I urge the same regarding abortion?" (1990: Abortion: Questions and Answers).
No issue is more fundamental than the right to life.
"In an age of artifice, many voters are hungry for substance. They admire and support political figures who speak out sincerely for their moral convictions. For our part we commend Catholic and other public officials who, with courage and determination, use their positions of leadership to promote respect for all human life" (US Bishops, Living the Gospel of Life, 1998, n. 31).
The present election cycle is no time for silence. "American Catholics have long sought to assimilate into U.S. cultural life. But in assimilating, we have too often been digested. We have been changed by our culture too much, and we have changed it not enough. If we are leaven, we must bring to our culture the whole Gospel, which is a Gospel of life and joy. That is our vocation as believers. And there is no better place to start than promoting the beauty and sanctity of human life" (ibid, n. 25).