SACRAMENTO, California – Starting Monday, a California law will require credit card networks like Visa and Mastercard to provide banks with special retail codes that can be assigned to gun stores to track their sales.

But new laws in Georgia, Iowa, Tennessee and Wyoming do just the opposite by banning the use of specific gun store codes.

The conflicting laws highlight one of the nation's most recent gun policy debates, which has been quietly developing and dividing state capitals along familiar partisan lines.

Some Democratic lawmakers and gun control activists hope the new retail tracking code will help financial institutions flag suspicious gun purchases for law enforcement, potentially preventing mass shootings and other crimes. Lawmakers in Colorado and New York have followed California's lead.

“The Merchant Category Code is the banking system's first step in saying, 'Enough! We're cracking down,'” said Hudson Munoz, executive director of the nonprofit advocacy group Guns Down America. “You can't use our system to facilitate gun crime.”

But many Republican lawmakers and gun rights activists fear that the sales rules could lead to unjustified distrust of gun buyers who have done nothing wrong. In the past 16 months, 17 states with Republican-led legislatures have passed measures banning or restricting the use of a firearms sales rule.

“We view this as a first step by gun control advocates to restrict the legal trade in firearms,” ​​said Lawrence Keane, senior vice president of the National Shooting Sports Foundation, an industry group that supports legislation to ban the use of the tracking code.

The new laws exacerbate a vast national divide on gun policy. Last week, U.S. Surgeon General Vivek Murthy declared gun violence a public health crisis, citing the rising number of firearm deaths, including more than 48,000 in 2022. The move was quickly criticized by the National Rifle Association.

The states have also taken opposing positions in other areas of gun policy. On July 4, for example, Republican-led Louisiana will become the 29th state to allow residents to carry a concealed weapon without a permit.

In contrast, Democratic-led New Mexico this year tightened laws for people without a concealed carry permit, requiring a seven-day waiting period to purchase a gun – more than twice the three-day waiting period for a federal background check.

State responses to recent mass shootings have also varied. In Maine, where an Army reservist killed 18 people and injured 13 others, the Democratic-led legislature passed a series of new gun restrictions. After school shootings in Iowa and Tennessee, Republican-led legislatures there took steps that could allow more trained teachers to bring guns into classrooms.

The spate of laws addressing category codes for gun deals addresses an aspect of electronic financial transactions that happens behind the scenes. The Geneva-based International Organization for Standardization sets thousands of voluntary standards for various fields, including category codes for all kinds of businesses, from bakeries to boat dealers to bookstores.

These category lists are distributed by credit card networks to banks, which assign specific codes to the companies whose accounts they manage. Some credit card issuers use the category codes for customer reward points.

The codes can be used by financial institutions to detect fraud, money laundering or unusual purchasing patterns that are reported to the U.S. Treasury Department's Financial Crimes Enforcement Network as suspicious activity.

Banks and other depository institutions filed more than 1.8 million confidential reports in 2022 reporting more than 5.1 million suspicious activities. About 4% of annual reports result in follow-up by law enforcement and an even smaller percentage result in prosecutions, according to the Bank Policy Institute, a trade group that represents major banks.

Stores that sell guns have traditionally been grouped with other retailers in merchant categories. Some have been classified as sporting goods stores, others as miscellaneous and specialty retail stores.

At the urging of New York-based Amalgamated Bank, which works with gun control groups, the International Organization for Standardization introduced a new four-digit category code for gun and ammunition transactions in 2022. Major credit card networks initially announced they would adopt it, but backed down under pressure from conservative politicians and the gun industry.

Munoz, who led the effort to establish the gun store code, pointed out that guns and ammunition for some of the country's deadliest mass shootings were purchased with credit cards.

The purpose of a gun dealer code is to identify suspicious patterns, such as a person who has rarely bought guns before but suddenly starts spending large sums of money at multiple gun shops in a short period of time. Once banks are alerted, authorities could investigate and potentially prevent a mass shooting, Munoz said.

The new law in California requires credit card companies to provide the gun code to banks and other financial institutions by Monday. They will then have several months to decide which of their business customers should be classified as gun stores and assign them new codes by May 1.

Visa, the country's largest payments network, recently updated its Merchant Data Manual to add the Firearms Code to comply with California law.

The Democratic-led legislatures in Colorado and New York also passed new gun laws this year, which are set to go into effect at the same time as the California legislation next May.

“If someone were to buy a large number of firearms for suspicious reasons, it would be very difficult to determine right now,” said Phil Ting, a Democrat and California state representative who supports the new law. “You wouldn't be able to tell if they were footballs, golf balls or basketballs.”

Even with a gun store code, there is no way to determine whether a particular sale is for a rifle, a storage safe, or another product such as hunting clothing.

State laws banning gun transaction codes have different effective dates, but generally allow state attorneys general to seek injunctions against financial institutions that use the codes, with fines of thousands of dollars.

The dealer code could lead to more people buying guns with cash rather than credit to protect their privacy, said Dan Eldridge, owner of Maxon Shooter's Supplies in suburban Chicago. Although his business has not yet been recategorized, Eldridge said he has already installed an ATM in his store.

“As harmless as it may seem, this code is an attempt to stigmatize gun owners,” Eldridge said. “But even more troubling is the concern that this is yet another attempt by the private sector to circumvent the ban that prohibits the federal government from establishing a gun registry.”

Republican Iowa State Senator Jason Schultz is sponsoring a bill to ban gun control laws, citing concerns that federal officials could gain access to financial institution data on gun store purchases and use that data to justify raiding gun owners' homes, violating their Second Amendment rights.

“The states will have to make a decision,” he said, “whether they want to follow California's example or support the original intent of the U.S. Constitution.”