The head of the FBI is upset. In James B. Comey's ideal world, FBI agents would be able to access everything on a person's smartphone as long as a judge had issued a lawful warrant. But technology companies are now selling devices that encrypt the user's data. There is no "backdoor" access. Only the user can decode its contents.

Hence the speech Comey is scheduled to give Thursday. "Mr. Comey will say that encryption technologies used on these devices, like the new iPhone, have become so sophisticated that crimes will go unsolved because law enforcement officers will not be able to get information from them," The New York Times reports. "The speech was prompted, in part, by the new encryption technology on the iPhone 6, which was released last month. The phone is the first one that thwarts intelligence and law enforcement agencies, like the National Security Agency, from gaining access to it, even if the authorities have court approval." (The iPhone 6 is not the first smartphone to offer default encryption.)

Comey's speech is part of a sustained effort to sway the debate over encryption, or what the FBI calls devices "going dark," thwarting efforts to solve robberies, kidnapping, and other crimes. Comey has pressed this point on network television:

In the interview that aired on “60 Minutes” on Sunday, Mr. Comey said that “the notion that we would market devices that would allow someone to place themselves beyond the law troubles me a lot.” He said that it was the equivalent of selling cars with trunks that could never be opened, even with a court order. “The notion that people have devices, again, that with court orders, based on a showing of probable cause in a case involving kidnapping or child exploitation or terrorism, we could never open that phone?” he said. “My sense is that we've gone too far when we've gone there.”

These concerns strike many people as reasonable. The notion that Apple in particular is behaving badly briefly found purchase with the brilliant legal scholar Orin Kerr. But Comey's arguments are ultimately misleading and wrongheaded, as Julian Sanchez of the Cato Institute explains in a definitive essay. The full text is worth your while. It begins with a brief sketch of some relevant history:

When the digital world was young, a motley group of technologists and privacy advocates fought what are now, somewhat melodramatically, known as the Crypto Wars. There were many distinct battlefields, but the overarching question ... was this: Would ordinary citizens be free to protect their communications and private files using strong, truly secure cryptography, or would governments seek to force programmers and computer makers to build in backdoors that would enable any scheme of encryption to be broken by the authorities? Happily for both global privacy and the burgeoning digital economy—which depends critically on strong encryption—the American government, at least, ultimately saw the folly of seeking to control this new technology. Today, you are free to lock up your e-mails, chats, or hard drives without providing the government with a spare key.

I'd add that you've long been free to buy a safe that opens only with your thumbprint, bury a treasure chest in a location known only to you, or write a diary in code. Jumping to the present, Sanchez debunks the notion that Apple or anyone else is setting an alarming new precedent with its encryption:

It is Apple’s backdoor access that was the aberration, even for Apple. If you encrypt your MacBook’s hard drive with Apple’s FileVault, or your Windows computer with Microsoft’s BitLocker, then unless the user chooses to send either company a backup copy of her encryption key, they can no more unlock those encrypted files than a bookbinder can decipher the private code you employ in your personal diary. Strong encryption is not even new to smartphones: Google’s Android operating system—the world’s most popular mobile platform, running on twice as many devices as iOS—has featured full-device encryption since 2011, and Google has never had backdoor access to those encrypted files. And, of course, there have always been a wide array of third-party apps and services offering users the ability to encrypt their sensitive files and messages, with the promise that nobody else would hold the keys.

Acknowledging that encryption may nevertheless be growing easier and more prevalent, in a way that will sometimes thwart law enforcement from solving crimes, Sanchez shows that the case against backdoors for law enforcement is nevertheless strong.