Baker disagrees.

"You can't debate our intelligence capabilities and how to control them in the public without disclosing all of the things that you're discussing to the very people you're trying to gather intelligence about," he said. "Your targets are listening to the debates." In fact, he continued, they're listening particularly closely. For that reason, publicly debating intelligence techniques, targets and limits is foolish. As soon as targets figure out the limits of what authorities can touch, they'll change their tactics accordingly. In his view, limits should be set in secret. A class of overseers with security clearances can make the necessary judgment calls.

Trevor Timm, co-founder of the Freedom of the Press Foundation, attempted to defend normal democratic debate. "What separates us from countries like Russia and China is that we can have these types of debates with an informed public that are completely aware of what types of surveillance are available to governments and what the legal standards are," he argued. "We're not specifically debating who the NSA is going to spy on, but whole surveillance regimes. If we didn't debate that in this country, the Fourth Amendment would be classified. But it's not."

Then again, the Fourth Amendment could be classified.

Jonathan Abel has written about retroactive classification, "a little-known provision of national security law that allows the government to declassify a document, release it to the public, and declare it classified later on." The government could "hand you a document today and prosecute you tomorrow for not giving it back," he explains. "Retroactive classification can even reach documents that are available in public libraries, on the Internet, or elsewhere in the public domain."

What if an unclassified Fourth Amendment was a pre-9/11 luxury? Knowledge of its contours would take many years to fade. But if its text and opinions interpreting it were scrubbed from the public record, if Fourth Amendment jurisprudence were conducted behind closed doors going forward, so that a secret body of law could develop, the next generation of terrorists wouldn't know the limits of the state in future years.

Whereas right now, judges openly set forth limits—including limits on particular surveillance methods (like GPS car trackers)—for everyone including al-Qaeda to see! A terrorist with American citizenship is especially positioned to exploit this knowledge.

Transparency is, in that sense, terror-enabling.

Of course, if the Fourth Amendment and the law surrounding it is kept secret from terrorists and criminals, it would have to be kept from law-abiding Americans too. But like Baker says, the limits of surveillance can't be debated in public without better informing terrorists. And that leaves Americans with an important decision.