Story highlights Immigration and Customs Enforcement sought bids for a license-plate tracking database

Database would have been able to see where a vehicle's plate had been captured on camera

Tool would have helped law enforcement find criminals, one proponent says

Database would have violated the privacy of innocent people, ACLU argues

Homeland security officials on Wednesday abruptly shelved a proposal to build a national database of license-plate scans after criticism from privacy advocates.

The proposal, which had been posted online last week by the office of Immigration and Customs Enforcement, sought a contractor who could establish a searchable database of license plates, with the times and locations where they were spotted by traffic cameras and other sources.

But in a statement late Wednesday, the department announced a reversal.

"The solicitation, which was posted without the awareness of ICE leadership, has been canceled," said spokeswoman Gillian Christensen. "While we continue to support a range of technologies to help meet our law enforcement mission, this solicitation will be reviewed to ensure the path forward appropriately meets our operational needs."

It was unclear whether the proposal was dead or was merely withdrawn for revisions.

Under the proposal, officers in the field would have been able to use their smartphones to look up a license plate and see every time and every place the vehicle had been spotted by a camera.

"The database should track vehicle license plate numbers that pass through cameras or are voluntarily entered into the system from a variety of sources (access control systems, asset recovery specialists, etc.) and uploaded to share with law enforcement," the original solicitation read.

The proposed National License Plate Recognition database was to have been used by immigration officers to find and arrest fugitives.

Supporters of license-plate scanning, like former New York state homeland security chief Michael Balboni, said it could have been an invaluable tool for finding dangerous suspects.

"What license-plate readers have been used for most effectively is (trying) to do hits against outstanding warrants, against unlicensed drivers, against folks who have shown before that they've been involved in some kind of crime -- that's where the hits come."

But since the solicitation was posted and featured in the Washington Post, privacy advocates have warned that the database sounded like a dragnet that would track the whereabouts of all drivers, including people who have done nothing wrong, and that the records might be held indefinitely.

"The idea is, we want to collect everything on perfectly innocent people and then dip into it whenever we feel like it," said Kade Crockford of the American Civil Liberties Union. "There have already been quite a few cases of abuse. Essentially, the problem is that this is creating a nationwide warrantless location-tracking list."

Opponents also said the tracking of cars would reveal personal information about drivers, like whether they went to church, where they slept at night, or whether they had been to an abortion clinic or a political protest.