D.C. Mayor Vincent Gray pledged this week to review his police department's policy of throwing drivers in jail over expired vehicle registrations, following a FoxNews.com report on the practice. 

The mayor addressed the controversy in a letter Tuesday to Sen. Jim Webb, D-Va., who days earlier had complained to Gray that "there is absolutely no justification" for arresting motorists over expired tags. 

"I agree that imprisonment may be perceived as quite harsh for this type of violation," Gray wrote back, saying he'll review the law to see "if another option would be more appropriate." 

Gray suggested the police department could impound vehicles for the offense instead of arresting drivers. 

The response comes after several drivers came forward to complain about being jailed for what in most jurisdictions is a violation punishable by fine, not jail. 

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FoxNews.com last week reported on the practice; Webb cited the report in calling for a review. 

AAA has also raised concern about the policy, and on Monday relayed the case of a naval officer who apparently wrote Webb about being arrested for expired tags this past July. 

According to AAA, the arrest came as the officer and Naval Academy graduate was applying for renewed security clearance for an upcoming deployment to Afghanistan -- in that process, he was asked if he was ever arrested. 

"I obviously now have to answer the question yes and will have to for the rest of my life," he wrote, according to AAA. 

Gray, in his letter to Webb, defended the police department's policy, saying vehicles that don't have proper registration are a "potential threat." 

"It is important, especially in a city like the nation's capital, to ensure that we do everything we can to ensure the safety of the city," Gray wrote. 

He noted that the department currently allows a 30-day "grace period." Drivers whose tags are expired by fewer than 30 days can receive a fine. After that, they can be jailed. 

In pledging to review the practice, Gray said he would work with the D.C. Council "if an alteration to the law is needed."