If you’re concerned about the dragnet nature of the National Security Agency’s surveillance programs, then you should also pay attention to what your local police department is doing. You may find that the dragnet surveillance happening there has a lot in common with the NSA’s mass collection of phone log data.

More and more when it comes to monitoring the public, capability is driving policy. The limits of law enforcement surveillance are being determined by what is technologically possible, not what is wise or even lawful. And it’s not uncommon for the police to use a new technology in secret for as long as they can, and then allow the courts to sort out legality once the issue finally comes before them.

It has never been so cheap and so easy for our law enforcement agencies to access and record the details of our daily lives. Consider automatic license plate readers: This seemingly innocuous technology snaps photos of passing cars’ license plates and stamps them with the location, date, and time. While these scanners were once limited to uncontroversial purposes such as identifying stolen vehicles, increasingly the police save the photos for months or even years—even though virtually all of people whose movements are being recorded are completely innocent, and even though travel patterns can reveal sensitive details of our lives.

License plate readers are just one example of a mass surveillance technology that is spreading quickly. Surveillance cameras have become all-too-common in America’s large cities , but they may be eclipsed when more powerful video cameras are mounted on unmanned drones with the capacity to stay airborne for long stretches of time. The ARGUS-IS is a camera that can take high-resolution video of an area 15 square miles.

And that cell phone in your pocket? The police can get all of your location history very easily—without a warrant. In this case it’s not the government collecting everyone’s data, but cell phone service providers, who keep it for years. Why are they doing that? Because they can. Should they be doing that? No.

So when you think about dragnet surveillance, you should think about the NSA. But you should also worry about what your local police are doing with the data they collect about you.

One piece of good news is that some powerful members of the law enforcement community are publicly stating that surveillance capabilities should not drive policy. At last week’s conference of the International Association of Chiefs of Police, Philadelphia Police Chief Charles Ramsey reflected on the rapid development of technology and remarked, “We have to remind ourselves—just because we can do something doesn't mean we should do it.”

That’s exactly right. Equally important, law enforcement agencies should not attempt to conceal the use of technologies of mass surveillance. These tools, which by definition involve the collection of data overwhelmingly of innocent people, should be public because such dragnet surveillance programs implicate serious privacy concerns. We and our elected representatives have a crucial role to play in determining which uses are appropriate and which ones cross the line. Not only our country as a whole, but also the police, will be better off in the long run if we have an open debate about what today’s technology can do, versus what it should do.