Under new regulations set by the Transportation Department on Friday, it has become much more challenging for non-U.S. citizens to secure a commercial driver’s license.

Following a tragic accident in Florida last month, caused by a truck driver executing an unlawful U-turn, Transportation Secretary Sean Duffy stated that a subsequent audit revealed the previous regulations were insufficiently stringent, with several states not applying them uniformly. According to Duffy, the driver involved in the crash should never have been granted a commercial license due to his immigration status.

The inquiry discovered that commercial driver’s licenses were wrongly issued in states including California, Colorado, Pennsylvania, South Dakota, Texas, and Washington. However, Duffy highlighted that the issues were particularly severe in California, threatening to withhold $160 million in federal funding.

Here’s what is changing and what led to the changes:

Florida crash put the spotlight on immigrant drivers

The comprehensive audit was initiated after Harjinder Singh, a truck driver originally from India, made an illegal turn on Florida’s Turnpike, compelling a minivan to collide with his truck’s trailer, resulting in the deaths of the driver and two passengers, as reported by the Florida Highway Patrol. Singh and a passenger in his truck sustained no injuries.

Singh, who resided in California, initially obtained a commercial driver’s license in Washington before California issued him one. He now faces three state charges of vehicular homicide along with immigration violations.

Singh’s attorney, Natalie Knight-Tai, declined to comment immediately on the case.

Authorities have also addressed two additional fatal accidents this year involving immigrant truck drivers who allegedly should not have been licensed. In Texas, a driver failed to brake, causing a 17-car pileup that resulted in five fatalities. In Alabama, a driver hit four vehicles at a red light, leading to two deaths.

Crash and investigations incite heated political fight

The Florida crash and subsequent investigations have fueled arguments between the governors of Florida and California while eliciting outrage from President Donald Trump and Transportation Secretary Sean Duffy.

Duffy said the audit found instances in which California, Colorado, Pennsylvania, South Dakota, Texas and Washington issued licenses improperly, saying the rules need to be stricter.

But he has homed in on California, where he said investigators found that one in four of the 145 commercial drivers licenses for noncitizens issued since June that they reviewed should have never been issued under the current rules. California now has 30 days to audit its program and present a plan for complying or risk losing its funding.

California has pushed back on these claims, with a spokesperson for Gov. Gavin Newsom saying Duffy doesn’t understand federal law and claiming that commercial driver’s license holders from California have a significantly lower rate of crashes than both the national average and the Texas average, which is the only state with more licensed commercial drivers.

Duffy had previously threatened to strip some federal funding from California, Washington and New Mexico after he said they didn’t enforce English proficiency requirements for truckers that went into effect this summer.

California has been a battleground for the Trump administration, with the president and Newsom regularly taking to social media to air their grievances about the other.

Immigrants will have a hard time getting commercial licenses

The new rules only allow noncitizen drivers who have three specific visas to qualify. And states will be required to verify their immigration status. Only drivers who hold either an H-2a, H-2b or E-2 visa will qualify. H-2B is for temporary nonagricultural workers, while H-2a is for agricultural workers. E-2 is for people who make substantial investments in a U.S. business

The licenses will only be valid for up to one year unless the applicant’s visa expires sooner than that.

Officials said that out of 200,000 noncitizens who currently have commercial licenses, only about 10,000 of them would qualify under the new rules. But the rules aren’t retroactive, so those drivers will be able to keep their licenses at least until they come up for renewal.

All states must pause issuing commercial driver’s licenses to noncitizens until they can comply with the new rules.

Will this worsen the shortage of truckers?

The 200,000 noncitizen truck drivers on the road represent about 5% of all the commercial drivers. Duffy said he thinks there are enough American drivers to deliver all the loads.

Removing noncitizen drivers from the industry could force trucking companies to increase wages for entry-level operators and draw more job seekers, said Jonathan Marques, founder of the Driving Academy in Linden, New Jersey.

Marques said that could even make the industry more attractive.