Unsolicited robocalls have evolved from irritating to maddening since a March 2018 court decision put an end to the Obama-era Federal Communication Commission’s 2015 rules intended to curb them. But this week lawmakers discussed a newly proposed deterrence to tackle the disruptive auto-dialed spam calls: the threat of criminal prosecution.

“No one is immune to these illegal and potentially dangerous calls,” Sen. John Thune, R-S.D., said during a Senate Commerce, Science and Transportation subcommittee on communications hearing Thursday. During the hearing, he extensively discussed the Telephone Robocall Abuse Criminal Enforcement and Deterrence, or TRACED Act—bipartisan legislation he introduced with Sen. Edward Markey, D-Mass, this year.

“A credible threat of criminal prosecution is necessary and appropriate for those who knowingly flout laws to prey upon the elderly and other vulnerable populations,” Thune said.

A report released by the FCC in February found that nearly 48 billion robocalls were made to U.S. phones last year and that the number of complaints around illegal robocalls has been on the rise since 2015. The FCC further predicted that, in 2019, nearly 50% of all calls made to American mobile phones will be spam.

“The TRACED Act mandates that federal law enforcement, state attorneys general, and telecommunications experts work together to determine what systems and what potential modifications to our laws will create a credible threat of prosecution and prison for those who intentionally violate the law,” Thune said.

The bill also aims to crack down on a technique known as “spoofing,” in which scammers trick victims by displaying fake caller I.D. information. The TRACED Act would require the FCC to adopt “an industry-developed framework for call authentication.”

Presently, robocallers risk the threat of paying penalties to the FCC if they are caught. But during the hearing, Sen. Brian Schatz, D-Hawaii, noted that last year the FCC collected only $7,000 of the $208 million it fined to unlawful robocallers.

Representatives with front-line experience combating the pesky calls said interagency cooperation at the state and federal level paired with criminal prosecution are necessary to stop unlawful and often recidivist robocallers.

“I wholeheartedly agree with that view [that the threat of criminal prosecution is a necessary deterrent] and I applaud the TRACED Act for what it does in establishing an interagency working group to facilitate that type of criminal enforcement,” witness Kevin Rupy, a partner in Wiley Rein LLP Telecom, Media & Technology Practice, said. “The best way to prevent illegal robocalls is to stop them from ever being made and the best way to ensure that is to put the people that are making them behind bars.”

Nebraska’s Attorney General, Doug Peterson, who led statewide efforts in support of the bill, agreed. “A lot of these violators perceive it that way—when you are fined, you move on—but I think when you bring up criminal penalties, that’s when you’ll get their attention,” he said. Peterson also added that enabling state attorneys general to work together and directly with the FCC is a critical element in combating the problem.

“I think by working together we will be strengthened in enforcement,” he said.

The Commerce Committee unanimously approved the TRACED Act last week and the bill is moving to the full Senate for a vote.