The D.C. Council unanimously agreed Tuesday that motorists caught driving with expired license plates should not be sent to jail, revamping a controversial four-decade old law that had gained national attention.

With limited debate, the council approved emergency legislation proposed by Mayor Vincent C. Gray (D) that instead requires drivers with expired tags to be fined or have their cars impounded until their vehicle registration is brought up to date.

“Today, we have an opportunity to fix a problem in our law, one that has caused many people to scratch their heads in amazement,” said Council Chairman Kwame R. Brown (D), who introduced the legislation on behalf of the mayor.

Under a 1973 law designed to aid police in the fight against drugs and gangs, District police officers had been empowered to arrest someone if their plates were more than 30 days out of date. Although it was rare for a judge to sentence an offender to jail, those arrested often were fingerprinted, photographed and put behind bars for a night until their case could be heard.

The law, which D.C. police union officials claim has been a vital crime-fighting tool, gained national attention this month after Sen. James Webb (D-Va.) learned of it. In a letter to Gray, Webb said the District had “absolutely no justification for jailing citizens whose only offense is an expired tag.”

Gray agreed, and instructed police two weeks ago to limit or halt their enforcement of the law until the matter could be reviewed. Under the emergency legislation approved Tuesday, a motorists whose tag has been expired for 30 days or less will now face a $100 fine. Those with tags that have been expired for more than 30 days will face a $250 fine and could have their car impounded.

John B. Townsend III, head of public and government affairs for AAA Mid-Atlantic, called the revisions to the law “a matter of justice.”

“This puts an end to one of the most controversial traffic laws in the country,” Townsend said. “The fact that police officers were routinely arresting motorists for a simple traffic infraction strikes many law-abiding citizens and legal observers as being unseemly and over-the-top.”

But in an op-ed published in the Washington Post on Sunday, a leader of the local Fraternal Order of Police wrote the law has been “long-standing and effective.”

“Such arrests are a valuable tool for tracking down criminals and ensuring compliance with the District’s motor vehicle requirements,” wrote Kristopher Baumann,. chairman of the lodge’s labor committee

Baumann questioned whether Gray and Brown, both of whom are facing federal investigations into their political campaigns, reacted too hastily due to political pressure.

Yet, before the council vote, Council member Phil Mendelson (D-At large) said he has received assurances from Police Chief Cathy L. Lanier that the law could be altered without jeopardizing public safety.

“She is comfortable this is not necessary for good law enforcement,” said Mendelson, chairman of the Committee on Public Safety and the Judiciary.