Once upon a time, privacy was everyone's default setting. Imagine an era when most letters and ledgers existed only in a single hard copy, when long-distance communication was slow and unreliable, when unpickable locks existed and cameras didn't.

These are the conditions under which America's founding documents were written. It was far from a golden age, but there were undeniable upsides to a government that had neither the technology nor the resources to know what most people were up to most of the time.

Those days are done. Privacy is dead. We have killed it, you and I.

It happened slowly and then all at once, much like falling in love. We traded away some of our privacy for convenience, with credit cards and GPS and cloud computing and toll transponders. Some of it was taken from us while we weren't paying attention, via warrantless wiretaps and IRS reporting requirements and airport searches.

I applaud the valor of those who are fighting the rearguard action on privacy, making it their business to blow up bridges and burn crops as the rest of us beat a retreat. There are still many good opportunities to slow the rate at which the state gobbles up all privately held information about our purchases and daily routines and inboxes.

I used to think there might be some way to erect a legal bulwark between the ravenous state and the vast troves of private data. I now think that is a losing battle, primarily thanks to the too-common eagerness of the firms we entrusted with our intimate information to hand it over to law enforcement without even the formality of a warrant.

So we cannot keep our secrets much longer. But there is still hope. A minimal state where civil liberties are expansively interpreted and scrupulously protected offers the best chance to preserve the sphere of individual liberty. It matters much less if the state knows everything about you when it has no cause and no right to act on that information unless a genuinely serious crime has been committed.

If speech and assembly and trade are not crimes—not punishable by the state—then the loss of privacy will be less acutely felt. This, in turn, is self-reinforcing. A state where civil liberties are robust and jealously guarded has little reason to install a vast surveillance network of its own or to force its way into private networks. There is little it can do with that information. It's a virtuous cycle.

In other words, while the fight for privacy is over, the battle for civil liberties is more important than ever.

Nowhere is this lesson more apparent than in Hong Kong this summer. For months, there has been riotous protest in the streets over a bill that would allow the extradition of suspects to, among other places, mainland China—a nation not famed for its commitment to due process.

In the Joint Declaration of 1984, after the U.K. returned Hong Kong to China, the city was promised "a high degree of autonomy." Among the protected rights of Hong-kongers: "those of the person, of speech, of the press, of assembly, of association, of travel, of movement, of correspondence, of strike, of choice of occupation, of academic research and of religious belief."

This list of rights is familiar to Americans and to other members of the Anglosphere and reminiscent of our own Bill of Rights. Under this regime, Hong Kong has flourished. But in recent years, China has looked for ways to assert its power and incept its authoritarian political culture into one of the freest places in the world. This summer's extradition bill was the last straw.

The technology of protest in Hong Kong is striking. The citizens in the streets wear helmets, masks, glasses. They move under cover of umbrellas, faces and gaits obscured. They buy their train tickets in cash. The getup is practical and it looks quite cool, but it is nothing less than a MacGyvered right to privacy, snatched back temporarily from the ascendant surveillance state.

Hongkongers pull down lampposts, which are rumored to contain a full suite of surveillance technology, much as Iraqis pulled down statues of Saddam Hussein in 2003 or Hungarians pulled down monuments to Stalin in 1956. Authorities in Hong Kong admit the lampposts have the hardware necessary for spying but pinkie promise that they have disabled the continuous audio and video collection, the license plate logger, and the facial recognition tools.

To protest under threat of extradition to China is especially brave. Hongkongers know well that China is ruthless in stamping out dissent, and the protesters have every reason to believe that to be identified as a participant in the demonstrations could be very dangerous in the aftermath if they do not win the day.

But it's worth noting that their demands do not include a rollback of surveillance; it's far too late for that. Instead, they are insisting on due process, transparency, and democratic reforms. What matters now is not privacy—the masks and umbrellas are a stopgap while the city is in a liminal zone—but civil liberties.

Civil liberties work together. They support and reinforce each other. The possibility that any person could be hauled in to the mainland on vague charges and never heard from again makes the fine language about all the other rights in the Joint Declaration void.

What is fascinating is that so many people in Hong Kong seem to know that and to be willing to fight for it. Some estimates place 1 in 4 Hongkongers out at the protest—a truly astonishing number when the consequences of participation could be so dire.

But civil liberties do not function as flawless interlocking clockwork, with each burnished gear clicking into place to power a free society. Instead, they act more like an ecosystem, with complex and sometimes obscure interrelations between the components, evolved over time. Sometimes you don't know about a crucial symbiosis until it's already too late. The relationship between the rights protected in America's First and Second Amendments, for instance, has long been debated. To give up a little freedom of speech, to stop protecting some gatherings, to abridge due process in the most extreme cases can sound reasonable. But it could also be the disruption that destroys a delicate balance and sets off a cascade of destruction.

Sometimes, though, the system proves surprisingly robust. This can be true even when it's planted in foreign soil or tested by a vigorous invasive species, as the example of Hong Kong's history proves.

This is why Reason is absolutist about the protection of that high degree of autonomy from the state guaranteed by Hong Kong's founding documents, and ours. This is why we return over and over to the idea that the best defense from tyranny is a small state with a limited mandate to protect against force and fraud. It is why we insist on the distinction between true crimes and victimless crimes. It is why we are constantly asking what the unintended consequences of regulation will be. It is why we favor devolution and self-governance. It is why we demand transparency and fairness from our criminal justice system.

When the state can see everything—and it can, or will be able to quite soon—the only way to preserve a free society is to shrink the government's purpose and constrain its powers.

If Hong Kong is China's best-case scenario for personal freedom, the Uighur areas in the west are the worst case. The country's ethnically separate Muslim population now resides in an open-air prison, with mandatory facial scan checkpoints, tracking software forcibly installed on every phone, and concentration camps for the noncompliant.

The Uighurs are at the terminus of authoritarianism. They have lost even the right of exit. They cannot retreat to the mountains or smash their phones or wear a mask or emigrate. Hong Kong is fighting tooth and nail to avoid the same fate. So must we.