One common complain on the left about conservative political views is that conservatives favor legislating morality. One thing they mean by this is the conservatives favor certain kinds of laws about certain kinds of issues that rely on a moral conception that differs from liberal moral views. For example, conservatives tend to favor laws that restrict abortion. Those who find abortion morally unproblematic complain that legislating morality is a bad idea, because legislators shouldn't declare what people should do on such issues.
I've always hated the expression, for a number of reasons, but one is that most laws legislate morality. Laws against murder enforce a moral standard that it's generally wrong to kill people. Laws against larceny enforce the moral standard that it's generally wrong to steal from other people. Laws against homosexual sodomy may pick out acts that not as many people think are wrong, but it isn't any more or less a legislation of a moral view than the uncontroversial laws that legislate morality.
It's another matter to restrict laws to outlaw harmful activity or to require consent for certain behavior that affects others. Some people mean just that when they say they oppose legislating morality. In other words, they oppose legislation against activities merely because those activities are morally wrong, and they require a further explanation of why they should be illegal: violation of consent or causing of harm. But harm and consent are moral reasons for favoring laws against such things, so it's still legislating morality. It may be that only certain moral reasons are the sort to justify laws, while others are not, but it's not entirely helpful to make this point by saying you oppose legislating morality. It's a confused way of making the point, and clarity would be served by making clearer distinctions among different aspects of morality.
To be consistent, such a view requires major revisions to our laws. We'd have to remove motorcycle helmet laws, unless it could be argued that the only purpose of such laws is to protect anyone who crashes with a motorcycle from greater liability for the greater amount of damage caused by not wearing a helmet. But that can be more easily achieved by holding those without helmets more liable for damage to themselves rather than fining them for not wearing a helmet. Helmet laws are designed to protect people from themselves, not to protect them from harming others. Even if we expand the legitimate class of laws to include such paternalistic laws, we'd still have lots of laws that might be called moralistic beyond harm to others, harm to self, and consent.
For example, laws against cannot be fully justified by the harm they cause to potential offspring or the fact that minors can't legally or morally consent. A brother and sister who want to have sex with each other can sterilize themselves to remove the possibility of harm to offspring, and they can consent if they're old enough. Why should we have laws against such sexual acts if the only issues that should affect legislation are harm and consent? One might argue that there's psychological harm from incestuous sex, but we don't outlaw everything that might cause psychological harm, and I think the argument that it causes harm might depend on the prior moral view that it's wrong to engage in incestuous sex. After all, there's a parallel argument that gay sex or even heterosexual pre-marital sex causes psychological harm. These are just a few examples. Our legal system would need some serious revision if we want to apply this approach to moral justifications for laws in any consistent way.
It occurred to me, though, that there's another reason the political left should generally resist speaking in terms of legislating morality. The left tends to favor a view of the role of judges that conservatives often call "legislating from the bench". Once you look at what's going on, you might even be willing to call it "legislating morality from the bench". Rasmussen conducted a poll during the election last fall that correlates views on the role of judges with votes for Obama and McCain. The question read: "Should the Supreme Court make decisions based on what's written in the Constitution and legal precedents or should it be guided mostly by a sense of fairness and justice?" 82% of McCain voters and only 29% of Obama voters took the first option, while 29% of McCain voters and 49% of Obama voters took the second option. For the record, President Obama himself has said that in the cases where the justices disagree strongly it should be the second option (but he strangely thinks this is only 10% of the cases that they disagree strongly, when it's a lot more than that).
Insofar as a judge's role is to interpret the law, the judge should indicate what the law means and enforce it even if the judge disagrees with the law. Justice Thomas exhibited such a role in his dissent to Lawrence v. Texas, the Supreme Court decision that banned laws prohibiting homosexual sodomy. Justice Thomas thought such laws were stupid. He wrote a separate opinion from Justice Scalia's dissent just so he could say that. It was a short opinion. His opposition to the majority wasn't because he thought it was a good idea on policy grounds to have laws against homosexual sodomy. It was just that he didn't think the Constitution prohibited such laws.
Insofar as a judge's role is to administer justice, on the other hand, it seems that the judge's obligation is to administer morality and enforce it in the cases where the law is not clear or is indeterminate, and what that amounts to is basically legislating from the bench, in particular legislating morality from the bench. If the standard liberal complaint is correct that it's bad to legislate morality, it becomes extremely hard for me to see how a judge should do exactly that by determining the just outcome when the laws don't settle what should be done. Even though this isn't strictly speaking legislation, it's equivalent to legislating in its effect, which is why the term "legislating from the bench" has seemed so apt to so many. It certainly does seem equivalent to legislating morality as far as I can tell, and it's a highly-regarded role for judges among those on the leftward side of the political spectrum. It gives me even less reason to be patient with those who complain about legislating morality.