You can't blame police departments if they feel a trifle besieged these days. But police departments cannot blame anyone but themselves for that circumstance. They keep pushing the envelope—as a recent exposé of phone-data collection in southeastern Virginia demonstrates. (More on that momentarily.)

New York has largely abandoned its experiment with stop-and-frisk, in no small part because its results proved disastrous: Only 2 percent of stops uncovered contraband. That amounts to a 98 percent failure rate—even though officers ostensibly stopped only those who, based on their vast law-enforcement experience, looked suspicious.

The Ferguson, Missouri, police department's heavily armored response to riots in August provoked a national backlash against the militarization of domestic law-enforcement agencies. When they learned how many small-town police departments had been outfitted with mine-resistant armored personnel carriers, flashbang grenades, sniper rifles and other materiel of war, even many law-and-order conservatives decided things had gone too far.

Virginia's previous Attorney General, Ken Cuccinelli, certainly qualifies as a law-and-order conservative, perhaps more so than just about anyone. But last year Cuccinelli issued an opinion warning law-enforcement agencies not to stockpile data from license-plate readers, as many had been doing. Such data could be collected, he said, only if it were directly related to a criminal case.

Virginia legislator Mark Cole is another law-and-order conservative. But as noted in this column a week ago, he has introduced legislation to rein in the abuse of civil asset forfeiture, which allows authorities to confiscate houses, cars, and money from citizens without ever charging them with a crime. Cole says such policing for profit is "simply un-American."

And last year Virginia's conservative state legislature passed, and its conservative Republican governor Bob McDonnell (another former attorney general) signed, a two-year moratorium on the use of aerial drones by law enforcement.

Now comes news from the Center for Investigative Reporting that five police departments in Hampton Roads have been collecting and sharing cell-phone data. The information—shared by the departments in Hampton, Newport News, Norfolk, Chesapeake, and Suffolk—comes from subpoenas to service providers and from cell phones that have been seized in the course of an arrest.

The State Police had an opportunity to join the program, known as the Hampton Roads Telephone Analysis Sharing Network. It declined, according to the Norfolk Virginian-Pilot, "because of concerns about its legality." The State Police worried that the program was forbidden by the Government Data Collection and Dissemination Practices Act—the same law that formed the basis for Cuccinelli's warning against dragnet collection of license-plate data.

What's more, a unanimous Supreme Court ruled this summer that the police must obtain a warrant to download data from a suspect's cellphone. The Hamton Roads network participants aren't doing that. Moreover, the departments are sharing information from the database upon request. Kelvin Wright, the police chief in Chesapeake, stresses that the requests must have a specific investigative purpose. But that's not good enough. As a lawyer for the Virginia ACLU pointed out: Not only is a warrant necessary for the first look at the contents of a seized phone, a new warrant is needed if a second agency wants a look.

The five law-enforcement agencies are maintaining a cone of silence about the program, which is run by the Peninsula Narcotics Enforcement Task Force. (Chalk up another dubious victory for the War on Drugs.) A spokesman for the Hampton Police Department says providing details "could jeopardize ongoing and potential future investigations." Oh? Since we don't know what "potential future investigations" might investigate, it's hard to say what could "jeopardize"—whatever that means—those investigations. That amounts to an argument for never disclosing anything about almost any departmental policy—let alone eavesdropping.

Not that local elected officials seem very curious, mind you. The Hampton Roads Daily Press reports that neither the Hampton nor the Norfolk City Council even voted to join the data collection program. Both Newport News and Chesapeake included participation on their consent agendas—which are meant for routine, pro forma items—and approved it unanimously.

But localities in Virginia are nothing more than ministerial agents of the state, to which they must answer. So state legislators should demand a full accounting of the dragnet data program to clear up unanswered questions such as (1) whether it ever collects the content of text messages, Internet searches, and other cellphone features, or the metadata only; (2) how many citizens' data has been collected; (3) who else the data has been shared with, such as federal authorities or so-called fusion centers; (4) what legal authority the localities claim for collecting and sharing the data; (5) how long the data are kept; and (6) which specific crimes have been solved as a direct result of the data collection.

Too often, law-enforcement agencies claim sweeping powers and then justify them with vague assurances about their effectiveness that turn out to be false (see: frisk, stop-and). If you don't support a specific program, is the not-so-subtle implication, then you're aiding and abetting crime.

Bunk. People should not have to surrender either privacy or due process as the price of safe streets. Constitutionally guaranteed liberties might sometimes incommode the police. But law enforcement, as the term implies, is obliged to enforce the laws that protect civil liberties too.