In my FindLaw column today I argue that despite some flaws in its reasoning, Judge Marrero's ruling invalidating the gag order provision of the Patriot Act sensibly uses interests protected by the Fourth Amendment to bolster protection under the First Amendment. However, I note that this sort of "holistic" approach to the Bill of Rights, while sensible, is arguably inconsistent with the Supreme Court's ruling in Zurcher v. Stanford Daily. There the Court held that the fact that a search target was a newspaper could not be used to increase the level of Fourth Amendment protection it received.
In my FindLaw piece, I say that the Supreme Court's one-right-at-a-time approach is inconsistent with the original understanding and with the approach canonically favored by Justice Harlan in his Poe v. Ullman dissent. Here I want to suggest a further problem with this approach: It violates the spirit of the Ninth Amendment. Conservative judges and scholars hesitate to give the Ninth Amendment its most natural reading---protecting unenumerated rights---because they worry that once unmoored from the textually protected rights, courts will simply use the Ninth Amendment as a license to displace value judgments by the people's elected representatives with their own value judgments. Whatever the merits of that point, there is---or rather there should be---a different and less controversial use of the Ninth Amendment: It can act as a guide to the interpretation of the enumerated rights.
Although expressly concerned with the rights not enumerated, we can also read the provision to say something like the following: "Don't get all hung up on the exact wording of these rights." On this account, the "other[ rights] retained by the people" to which the Ninth Amendment refers include rights at the boundary of the enumerated rights. Using the Ninth Amendment to "interpolate" in this way (a term Larry Tribe and I used in our book On Reading the Constitution) should be less controversial than using it as the basis for "extrapolating" to other rights, because it is, to continue the spatial metaphor, closer to the enumerated rights, and thus less likely to give vent to judges' personal values.
Mind you, I'm not saying that extrapolation is illegitimate. I'm simply saying that if one worries that extrapolation runs counter-majoritarian risks, one need not worry (nearly as much) about interpolation. Thus, a right that falls somewhere between the First and Fourth Amendments could be cognizable by the courts even if it doesn't fit exactly within either Amendment standing alone.