The Unitary Post Office?
Here's a further thought regarding Thomas's very interesting post on Saturday (and the follow-up in the comments) regarding the President's claimed authority to open mail without warrants, notwithstanding the law that prohibits the practice. As the comments note, at least with respect to the "foreign" mail, there is a familiar, if not very persuasive, argument that Bush's authority as Commander in Chief excludes congressional limitations on his ability to engage in necessary military tactics, including espionage, and thus including intercepting mail of foreign origin. To be sure, that argument is itself undermined by the signing statement's reference to specific authorization for such Presidential snooping. If, as the Administration claims, this sort of thing is an inherent and unlimitable power of the President, then he should be able to do it with or without specific authorization. But let's put that issue aside. I'm more interested right now in the claims regarding the exigent circumstances exception, which are not limited to foreign-origin or national-security-related mail.
With respect to exigent circumstances, the signing statement does not, so far as I can tell, claim any inherent unlimitable authority. Bush doesn't argue that his powers as "Postmaster in Chief" cannot be limited by Congress, and for good reason. The Constitution does not make him the Postmaster in Chief. So his claim is simply that, as Thomas suggests, the statute's silence with respect to exigent circumstances should not be read to preclude warrantless searches justified by exigent circumstances. That claim sounds in the idea--fashionable among conservative activists as well as conservative and even some progressive/centrist legal academices--that whenever Congress writes an ambiguous statute, federal administrative agencies, rather than courts, should resolve the ambiguity. This idea is closely connected to the theory of the "unitary" executive because the chief argument is that agencies are politically accountable through the President, in a way that courts are not. (One could also justify the preference for agency decision making over judicial decision making on expertise grounds, but this approach has been out of fashion for a couple of decades.) Thus, in this case, the theory would go: the post office is a federal executive branch agency; therefore the Executive, rather than the courts, should construe the scope of its authority to conduct warrantless searches of the mail.
The difficulty with the foregoing argument is that the Post Office is a so-called "independent" agency, specifically designed by Congress NOT to take orders from the President. (See the statute here.) But for those, like the true believers in the Bush White House, who adhere to the strong form of the "unitary Executive" theory, the very notion of an independent agency is anathema. As part of the Executive Branch, they say, the Post Office must ultimately be controllable by the President. The Supreme Court bought a related argument with respect to a first class postmaster in the 1926 case of Myers v. United States but subsequent decisions have essentially gutted that ruling. Accordingly, it's not plausible to attribute to Congress the intent of making the President the authoritative interpreter of ambiguity in a statute limiting searches of mail.
Ultimately, at least with respect to the exigent circumstances point, this is probably a case of the President who cried wolf. We are so accustomed to Bush signing statements that either gut the statute passed by Congress or construe it to mean the exact opposite of what Congress likely intended that we have a hard time recognizing a reasonable interpretation when one comes along. It strikes me as utterly appropriate to say that there is an exigent circumstances exception to the requirement of a warrant to open mail. The statute does not rule one out and we can easily imagine an exigency in which it would be madness to delay for even a second to obtain a warrant: e.g., a piece of mail that smells of gunpowder and is ticking. To continue the wolf metaphors, this signing statement -- or at least the exigent circumstances portion of it -- may be a sheep in wolf's clothing.