It's never wise to expect much more than entertainment from a congressional hearing. And Attorney General Alberto Gonzales' appearance Monday before the Senate Judiciary Committee to defend the National Security Agency's program of warrantless wiretaps was not without its entertaining moments.

From the attorney general himself, the marathon inquiry produced plaintive cries that applications "an inch thick" were sometimes required to obtain formal wiretap authorization from a Foreign Intelligence Surveillance Court—a burden that hasn't stopped intelligence agencies from obtaining record numbers of such warrants since 9/11—and the eyebrow-arching suggestion that disclosure of the NSA program had aided al Qaeda because, in the absence of media coverage, "sometimes they forget" that the government is attempting to keep tabs on them. Unlike his Republican colleagues, who occasionally remembered that conservatives are supposed to retain a modicum of skepticism about unchecked government power, Sen. Jeff Sessions (R-Ala.) kept an indulgent smile plastered on his face through several rounds of interrogatory fellatio so shameless that "If you were a vegetable, Mr. Attorney General, what sort of vegetable would you be?" would have constituted a hardball question. And Sen. Russ Feingold (D-Wisc.) managed to ask about a dozen variants of "Why didn't you tell us during your confirmation hearings that you believe the president can break the law?"—apparently unable to wrap his head around the notion that Gonzales, correctly or incorrectly, doesn't believe the NSA program to have violated the law.

But amid all the folderol, the hearing did manage to sketch a decent overview of the case for the president's wiretap program. As Gonzales' testimony clarified, the analysis of the program's legality is actually a sort of constitutional Choose-Your-Own Adventure. If we want to know whether the NSA's warrantless wiretaps are legal, we first need to figure out in which of three possible realms of authority the president is operating. Once that question is answered, we can proceed to determine how broad the president's powers are in that realm.

To answer the first question, Gonzales acknowledged, we turn to the framework laid out by Justice Robert Jackson in Youngstown Sheet & Tube Co. v. Sawyer, in which the Supreme Court rejected Harry Truman's seizure of steel mills during the Korean War:

When the President acts pursuant to an express or implied authorization of Congress, his authority is at its maximum, for it includes all that he possesses in his own right plus all that Congress can delegate.... When the President acts in absence of either a congressional grant or denial of authority, he can only rely upon his own independent powers, but there is a zone of twilight in which he and Congress may have concurrent authority, or in which its distribution is uncertain.... When the President takes measures incompatible with the expressed or implied will of Congress, his power is at its lowest ebb, for then he can rely only upon his own constitutional powers minus any constitutional powers of Congress over the matter.

Fortunately, both sides of the debate agree that we are not in the twilight zone. Everyone agrees that Congress has spoken on the subject of wiretaps; the dispute is over what it said. If, as Gonzales and the administration contend, the Authorization for Use of Military Force (AUMF) passed by Congress shortly after 9/11 included (perhaps in invisible ink) the authorization to conduct wiretaps, the president is in the first realm. If it did not, the Foreign Intelligence Surveillance Act (FISA), which makes it a crime to conduct wiretaps without judicial authorization after the first 15 days of a war, places the president in the third realm, where "his power is at its lowest ebb."

Even in the former case, in which the president's power would be limited only by whatever restricitions the Fourth Amendment imposes, it is by no means obvious that warrantless wiretaps pass constitutional muster. Administration apologists are fond of citing a long history of wartime electronic surveillance by presidents as proof that this is part of the "inherent authority" of the executive. But as Sen. Feingold noted during the hearing, these examples typically precede not just FISA, but the Supreme Court's recognition in Katz v. United States (1967) that electronic communications are subject to any Fourth Amendment protection. Prior to that decision, it was taken for granted that not only the president but any police officer could conduct a wiretap without a warrant.

Proponents of broad presidential surveillance authority are fond of citing United States v. United States District Court (1972), in which the Supreme Court concluded that the president could not sidestep the warrant requirement for domestic surveillance just by crying "national security." Deploying logic similar to that of the lovelorn turtle in Shel Silverstein's poem "The Bagpipe Who Didn't Say No," they argue that because the Court exhibited restraint in explicitly refusing to consider the separate issue of surveillance involving agents of foreign powers, we should assume the president retains the power to authorize wiretaps in such cases.

Whatever the merits of that argument, it evades the key question of whether, in fact, the wiretaps being authorized do involve "agents of a foreign power." During Monday's hearing, the attorney general asserted that wiretaps are initiated only when intelligence agents have "reasonable grounds to believe that a party to communication is a member or agent of Al Qaida or of an affiliated terrorist organization," which Gonzales characterized as equivalent to a "probable cause" standard. Yet this weekend, The Washington Post reported that sources who'd pored over the communications of NSA targets "dismissed nearly all of them as potential suspects after hearing nothing pertinent to a terrorist threat," echoing a January New York Times article that found the vast majority of leads the program produced were dead ends.

Even some defenders of the program, such as Judge Richard Posner, writing in The New Republic, concede that the program makes sense only as an attempt to figure out who the "agents of a foreign power" are, since once that's known, there's no reason not to obtain a FISA warrant. But if the procedure for vetting searches systematically turns up far more dead ends than real terrorists, then it is pretty much by definition not a procedure embodying a probable cause standard. Insofar as that calls into serious question whether the NSA's internal checks meet the Fourth Amendment's "reasonableness" standard, it seems natural to conclude that the ordinary restraints on surveillance of U.S. persons should apply.

And that is the best case scenario for the administration. Even A.G. Gonzales conceded that if the president is operating in the third of Justice Jackson's realms—acting without congressional authorization and therefore against FISA—the permissibility of warrantless wiretaps becomes what Gonzales calls "a much harder question." The president may be commander-in-chief of the armed forces, but Article I, Section 8 of the Constitution reserves for Congress the power to "make Rules for the Government and Regulation of the land and naval Forces." It seems no great stretch to suppose that this includes laying out reasonable procedures intelligence agencies must follow in conducting wartime surveillance.

So which realm are we in? That question turns on the administration's claim that the AUMF—to the surprise of the legislators who voted for it—superceded FISA and gave the president broad powers to eavesdrop on communications between U.S. persons and suspects abroad. That claim is almost shockingly weak.

It's a hoary canon of legal interpretation that in the absence of "overwhelming evidence," you don't assume that a prior statue has been repealed or otherwise weakened, and that you don't trump very specific language, like that of FISA, with broader language, like that found in the AUMF. The crux of the administration argument that the AUMF nevertheless carved out an exemption to FISA is most fully articulated in a Department of Justice white paper that leans heavily on a strained analogy to the Supreme Court's ruling in Hamdi v. Rumsfeld, in which the Court signed off on the detention of American citizens captured on the battlefield as a " fundamental and accepted incident to war" by "universal agreement and practice," though not explicitly covered by the AUMF.

This is no great leap. The alternative is to suppose that enemy soldiers incapacitated in the midst of battle must either be permitted to return to the fray as soon as they've recovered or shot on the spot. Well, Gonzales and an enthusiastic Sen. John Kyl (R-Ariz.) argued, surely if we can shoot them, we can tap their calls, right?

This argument is doubly bizarre. First, it supposes that a massive program of domestic wiretaps is as obvious and natural an "incident of war" as holding enemy soldiers encountered on the battlefield. Second, it presumes that an American residing in the U.S. may effectively be treated just like that armed enemy soldier just on the executive branch's say-so, even when intelligence agencies have manifestly failed to distinguish innocent people from terrorists with any great precision.

Gonzales tried to bolster the AUMF argument on Monday by arguing that it was actually "more specific" than FISA because it pertained to al-Qaeda, while FISA dealt with wiretaps generally. That would be more plausible if Congress hadn't amended FISA after the AUMF (with nary a mention of the supposed exemptions created there) precisely to give intelligence agencies greater latitude to pursue terrorists.

If the administration's legal case emerged from Monday's hearing in less than sterling shape, its political position looked relatively robust. As several Republican senators smugly observed, Congress retains the "power of the purse" as a check on executive branch programs of which it disapproves, but no Democratic legislators have yet dared propose using that power to defund the NSA program. That only proves, as every teenager soon learns, that it's easier to ask forgiveness than permission—though the Bush administration appears congenitally incapable of even the former. As economist and political theorist Charlotte Twight has observed, the manipulation of political "transaction costs" has been a key to the growth of government power over the last century. A program that might never make it through Congress if both houses had to explicitly approve it might nevertheless prove politically impossible to halt once underway.

Gonzales' appearance before the Senate, then, amounted to an extended bluff with a weak legal hand. It only remains to be seen whether any legislators have the fortitude to call him on it.