Jeremy has a good post on the Ninth Amendment at "Parableman". It seems to me that the function of the Ninth Amendment is primarily to make clear the fundamental importance of the people: no one can appeal to the fact that the Constitution doesn't enumerate a right in order to infer that the people do not have it. The Constitution is a set of delegated powers and restrictions made by the people on the government: its purpose is to restrict the government (to the extent that this can be done and the national objects of union, justice, tranquillity etc. be met), not to restrict the rights of the people. A major worry about a bill of rights was the possibility that if any rights were left out, that would be an occasion for someone to argue that they didn't exist at all; preventing that is the basic rationale for an amendment of this sort.
Which is all well and good, theoretically; but how should it function practically? The key phrase for practical use should be the phrase "retained by the people". The way I think a court should regard the Ninth Amendment is this: the people have not retained some rights; the rights given up are those in which we have (in the Constitution) allowed the government to interfere with our lives. However, they have retained many rights, some of which are enumerated, some of which are not. The rights that are enumerated must be protected, simply speaking. As to the unenumerated rights, the point is basically this:
People can never be presumed by the government not to have a right, as long as it does not fall into the category of rights they have explicitly (in the Constitution) not retained.
Or, in practical terms: when it comes to determining whether the government can do a given thing, the burden of proof should fall on the government to show that in this action it remains within the field of Rights Explicitly Not Retained By the People. In other words, the real force of the Ninth Amendment should be to require that the government stay within its Constitutionally authorized bounds, and be able to show that it has done so. (The Tenth Amendment does something similar.)
I think Jeremy is right that attempting to parse the Ninth Amendment by enumerating the unenumerated rights is doomed to failure. It's on the right track, in the sense that the courts have the responsibility not to ignore the Ninth Amendment and the duty to take it seriously. But the best way to do that is not to enumerate the rights the people have retained, but to make clear that the government gets no free passes to do something merely because the Constitution doesn't explicitly say it can't; in other words, to make sure that the government only do what the Constitution says it can. The enumerated rights go one step further, since they have to be respected even where the government has been given power; and Jeremy is right, I think, that when it becomes necessary to enumerate a right (as it sometimes has been necessary), the way to do it is by amendment.(*) Indeed, as Jeremy notes, the only constitutional way to enumerate a right is by amendment. For other rights, the Constitution merely says we can't be presumed by the government not to have them.
(*) It occurs to me, though, as one possible exception to this, that people do have enumerated rights that are not enumerated in the U.S. Constitution: namely, additional rights enumerated in their State Constitutions. This, when combined with the Tenth Amendment, has the potential for special judicial bite. Thus, to take just one example, the Vermont Constitution explicitly gives the people (through their legal representatives) "the sole, inherent, and exclusive right of governing and regulating the internal police" of Vermont; it gives each member of society "a right to be protected in the enjoyment of life, liberty, and property," "a natural and inherent right to emigrate from one state to another that will receive them," and so forth. When the Ninth Amendment is combined with the Tenth Amendment, the effect is that residents of Vermont have certain enumerated rights, although they are not enumerated in the U. S. Constitution, that the federal government must respect in any matters to which both the Ninth and Tenth Amendments extend. Thus, even if one thinks the Ninth Amendment weak on its own, it has the potential for important effects when combined with other amendments.
