There’s an arms race playing out in Nashville, where lawmakers have been fighting for and against the rights of workers to take guns to work.

The Second Amendment spat began in 2013, when Gov. Bill Haslam signed into law the controversial “Guns in Parking Lots" bill. But the original law, which stated citizens with permits to carry guns can keep them in their cars on company property even if the employer bars them, only protected citizens against prosecution, not firing. The Tennessee Firearms Association dubbed the law the “Lose Your Job if You Commute Act.”

Now, pro-gun politicians say they have fixed the law.

“No employer shall discharge or take any adverse employment action against an employee solely for transporting or storing a firearm or firearms ammunition in an employer parking area,” reads an amended version of the bill, signed into law earlier this month by Haslam, a Republican.

“The employer cannot [fire you] simply because you have a permit or a gun in your car.”

- Tennessee Rep. Mike Carter

An estimated 500,000 residents of Tennessee have permits to carry guns, and in a state where hunting is popular, having guns secured inside a car is not uncommon. While employers usually would not know if cars in their parking lots contained firearms, there are ways it could be brought to their attention, according to University of Tennessee Law Professor Dwight Aarons.

“Maybe there’s a broken window in the car, or a drug sweep or somebody being careless where someone is talking too much, saying they have a gun in their car -- there are a thousand other different ways,” Aarons told FoxNews.com.

The amended bill had overwhelming support in Nashville’s GOP-dominated Statehouse, but was opposed by a coalition of groups that included Democrats, gun control advocates and the state Chamber of Commerce.

“It’s outrageous,” said House Democratic Caucus Chairman Mike Stewart, who told FoxNews.com businesses are now forced to allow people with weapons on their private property. “What’s next? Are we going to have a law that forces a family to let an armed person into their living room? Where does it stop?”

The law’s sponsors initially thought employees were protected, but then-Attorney General Robert Cooper, a Democrat, issued an opinion months after its passage that the law did not prevent employers from firing workers who brought guns to the job site.

Vice President of the State’s Chamber of Commerce Bradley Jackson said his group opposes the law because it sends a bad message to employers.

“It violates our personal property rights and tramples all over it,” said Jackson. “It’s going to be costly to defend in court,” adding the law also compromises business’ ability to maintain a safe workplace.

State Rep. Curry Todd, the Republican who sponsored the bill in the legislature’s lower chamber, said the new version clears up legal confusion. But fellow lawmakers were quick to say it can’t be used as a defense for employers fired with other justification.

“The employer cannot [fire you] simply because you have a permit or a gun in your car,” Republican State Rep. Mike Carter told The Tennessean. “But if you sue alleging that, you have to prove that was the sole reason you were terminated. If you were late to work and terminated, no dice,” said Carter.

Nearly 20 states have adopted laws that ban employers, including school districts in many cases, from restricting guns in their parking lots, according to the San Francisco-based Law Center to Prevent Gun Violence.

Kyle Rothenberg is a graduate of the Junior Reporter program at Fox News. Follow him on Twitter: @kylerothenberg