A move by Virginia legislators to limit the police use of data from automated license plate readers, and “any surveillance technology” used by law enforcement, hit a bump Friday afternoon when Gov. Terry McAuliffe (D) amended the General Assembly’s bill, provoking an angry response from the bill’s sponsors and setting up a showdown next month in Richmond.

The General Assembly overwhelmingly approved a bill last month which would require police to purge the data from license plate readers within seven days, unless they have a warrant or a pending criminal or terrorism case. The readers, typically installed on the back of moving patrol cars, photograph hundreds of license plates per minute and record the time and location each shot was taken. An instant check of databases can determine if a car is stolen or otherwise wanted, but police can also save the data and review it later to see if a suspect was photographed near the scene of a crime or to locate a missing person.

In 2013, the Virginia State Police asked then-Attorney General Ken Cuccinelli if maintaining the data was legal. Cuccinelli issued an opinion saying that the passive collection of the data was not legal under existing state law, without a direct link to an active case. The state police then began to purge their data within 24 hours, but police departments in Northern Virginia elected to ignore Cuccinelli’s opinion and keep the data for up to two years.

Civil libertarians balked at the possibilities for abuse and invasion of privacy by law enforcement, and after a story in The Washington Post revealed the ongoing practice by police, legislation was first introduced last year and a bipartisan privacy caucus was launched. This year, bills authored by Sen. Chap Petersen (D-Fairfax) and Del. Richard L. Anderson (R-Prince William) proposed not only a seven-day limit on data retention for license plate readers but “any surveillance technology,” to include body cameras, dashboard cameras, and any future technology police might devise. The legislation passed the Senate 38-0 and the House 95-4.

But on Friday, McAuliffe changed the seven-day limit to 60 days, and changed “any surveillance technology” to “license plate readers.” Brian Moran, the Secretary of Public Safety and Homeland Security, said Friday that he had “been informed by numerous law enforcement agencies that license plate readers result in salient and compelling information. The governor’s amendment…represents a significant compromise by law enforcement. The governor believes 60 days is a more appropriate period of time and reaches a compromise with the legislature that’s reasonable.”

Police had strongly lobbied the General Assembly against the bill, citing examples where crimes were solved or missing persons found, and were stunned by how little progress they made with typically receptive legislators. Prince William Chief Stephan Hudson said Friday that he was “grateful to Gov. McAuliffe for taking this step.  However, even 60 days falls short of our hopes for six months.  Across the D.C. region, all law enforcement agencies use LPR as a significant tool in providing protection to the nation’s capital and the surrounding areas.  Virginia is the only state around D.C. which limits LPR retention to this short a period of time.”

On amending “any surveillance technology” out of the bill, Moran said state officials were still studying the use of police body cameras and the retention of their footage, and that expanding a bill originally intended for license plate readers “I think is overbroad.”

Petersen said he felt McAuliffe’s language “guts the bill. I don’t look at it as a compromise, it’s essentially destroying the bill.” He said McAuliffe’s amendments “completely miss the point of the legislation…These surveillance technologies are Big Government infringing on the rights of Virginians to live their lives in peace without government scrutiny. Given the nature of these amendments, which defeat that right, I would have rather had the Governor veto the bill.”

Anderson called the governor’s actions “vetoing the bill by amendment.” He said in extending the data retention period to 60 days, “anything can happen in that 60 days. It creates a vast pool of data that is easily hacked, as we’ve seen elsewhere. And that’s a 60-day window for that stuff to migrate to God knows where.”

Anderson also predicted “a huge backlash from civil libertarians, the ACLU, the NRA,” all of whom aggressively supported the bill.

The bill now goes back to the General Assembly, which meets on April 15 to vote on whether to accept or reject the amendments. If the assembly accepts the amendments, they become part of the law. If the assembly rejects the amendments, the bill goes back to McAuliffe, who then must decide whether to sign or veto the original legislation.