Morality cannot be legislated, but can be reflected within the codification of law. All that should ever be done through legislation is the safeguarding of Rights. By prohibiting theft, the culture helps to insure property Rights, for example. By prohibiting murder, the culture helps to insure the Right to live. The question then becomes about the exercise of Rights, where one individual's end, and where another's begin. This is why the abortion issue is the most difficult one to balance.
Morality, by definition, is concerned with the difference between right and wrong or between good and bad behaviors, all of which are arbitrary and contextual, and ultimately why it cannot be legislated. However, the determination of where one's Rights end and where another's begin reflects the moral "standard."
Our Civil Rights laws, our Bill of Rights laws, our ammendment to leagl age laws, our employment laws, our disbility laws, our fair employment and housing laws, our poverty mitigating laws, our retirement and elderly laws all are legislated based upon morality.
It is immoral to limit or abuse people based on race or ethnicity. It is immoral to deny freedom of speech, protest, religion. It was seen as immoral to send 18-year-olds to Vietnam without giving them a say in their government (this one could be turned the other way and say the law was a pay-off for the immorality of drafting teenage boys into such a conflict). It is immoral to allow children to work as they did in the Industrial Revolution. It is immoral to leave Americans without some safety net when they loose their jobs. It is immoral to limit or hinder the freedom of disabled persons. It is immoral to deny a person employment and housing based on personal prejudice and bias. It is immoral to allow children to go without food, housing and medical aid. It is immoral to allow the elderly to go without provision and assistance.
As you can see, we can and we do habitually legislate morality. It seems to me that as our society grows ever more technologically complex with ever more distant horizons breached and with ever growing exposure to cultural dangers, we will need ever more legislation based upon morality. In fact, it may be said that the debate over legislation about illegal immigrants derives from both economic concerns and moral concerns.
I have to agree with post 3 that morality should be legislated when our choices affect others. Obviously, morality is a difficult thing to define and pin-point. I think each culture and each person decides what is morally right. Each culture and country will regulate their citizens based on their own definition of morality. Every culture regulates its citizens accordingly. I doubt that the finer points of morality can be regulated because each individual is going to differ on what they believe is morally right or wrong.
My initial response is to think how on earth do we decide on what is moral behaviour or not. Clearly, there are some basic moral norms that perhaps we can all agree on, but in a globalised world where every day we are becoming more aware of the (often violent) collision of different cultures, each of which has there own set of norms and values, how can we ever hope to agree on what is moral behaviour for all of us?
I honestly think that politicians and lawmakers need to stop worrying about abortion and gay marriage and start worrying about the economy. Now is not the time to spend all of that effort when our country is getting worse and worse.
Most laws presently on the books are rooted in widespread assumptions about what is moral and immoral. Thus, laws against theft are rooted in the common assumption that stealing is immoral. Similarly, laws against murder are rooted in the common assumption that it is wrong for one individual to intentionally kill another individual. It is when issues of morality are in widespread dispute that "legislating morality" becomes difficult and perhaps even impractical and unwise.
I actually think there is a difference between considering something "illegal" and "immoral." Personally, the morality part, to me, is very personal. Making an action illegal is precisely because morality cannot be legislated. Everyone who lives by a moral code typically has some sort of guideline (be it a religious book, a leader's suggestion, or an innate "conscience"), but for the government to dictate which of these guidelines is the one the laws will be written from is where the line becomes blurry. To me, legislation does not dictate things which are moral or immoral, but simply, legal or illegal. And this, for some, becomes the moral code, but I do not think it begins the other way around.
To what extent can it be? The 18th Amendment is the only one of our 27 Amendents that attempted to do so, and it failed miserably, as have drug laws, and laws against pre-marital and extra-marital sex. People have a way of determining for themselves what is and what is not moral, and only comply with those moral laws they agree with. Nor is there any clear definition of morality in many cases. Some might consider abortion a mortal sin, while others look at it as a medical procedure.
Morality should be legislated at the point where your actions harm or adversely affect other people. You have the right to your own opinions and beliefs, and the right to live your life the way you see fit, but you have no right to impose your beliefs, morals, or lifestyle on any other person against their will.
For example: every woman has the right to sex, birth control, and abortion without needing an excuse (rape or incest), but no one has the right to keep a woman from making her own decision. On the flip side, every woman also has the right to oppose abortion on religious or personal moral grounds, but no one has the right to tell a woman that her choice in abortion makes her evil, ungodly, or inferior.
Now, most people have no problem telling you just what they think, no matter how offensive it might be to you, but we do not have a right to be un-offended. We have a right to walk away and not listen. The right to speak is not the right to be heard; if you are offended by someone, choose to ignore them. This is not an issue that should be legislated.
On the other hand, if your personal beliefs include religiously sanctioned abuse of woman and children (or anyone at all), or inhumane animal sacrifice... well, I would say that crosses the line onto forcing your beliefs on others to their detriment, and should absolutely be legislated.
This is a very difficult question because almost every law is based on some sort of moral assumption.
For example, when we make laws against stealing, we are acting on a moral principle. This is the moral principle that says that people are entitled to their property and that it is wrong to take that property from them. When we legislate against child abuse, we are basing this on a moral system that we now have that is very different from the morals our ancestors would have had. Essentially every law we make is setting boundaries based on what we think is right and wrong.
In a sense, we have no choice. We have to legislate morality because it is very hard to prove in some objective way that stealing is wrong or that anything else is wrong absent some basic understanding of what morality is. So morality has to be legislated. We have to base our laws on morality.
I suspect, though, that you are asking about issues of what we might call personal morality. This would include things like homosexuality, perhaps, or drug use or perhaps divorce. Personally, I think that homosexuality is not a choice that people make and shouldn't be discriminated against. But I realize that that is an opinion I have based on nothing much more than my moral values.
One rule I might propose is that we should not legislate morality unless the actions that we think are immoral have a negative impact on other people. The trouble with this rule is that it is not easily applied in all cases. Many Christians think that gay marriage and divorce harm society. I don't think so, but that is once again due to my moral values and beliefs.
All laws are going to be based on someone's moral values. Therefore, it is impossible to say that we should not legislate morality. The trick comes, though, in deciding how far we should legislate morality.