(WXYZ) — The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives issued a public safety advisory Tuesday to all federal firearm licensed dealers (FFLs) in the state regarding a change in background checks.

In the letter, the ATF tells all Michigan FFLs that they are required to conduct a National Instant Criminal Background Check System (NICS) before selling a firearm to someone who doesn't hold an FFL, even if that person holds a Concealed Pistol License (CPL).

This changes a previous rule the ATF issued on March 24, 2006, saying that all FFLs could sell to someone with a valid CPL that was issued on or after Nov. 22, 2005, instead of running a NICS background check.

According to the ATF, Michigan State Police require a NICS check on anyone who applied for a CPL in the state, and that a CPL shall not be issued unless MSP "has determined through the federal national instant criminal background check system that the applicant is not prohibited under federal law from possessing or transporting a firearm [and] has verified through the United States Immigration and Customs Enforcement databases that the applicant is not an illegal alien or a nonimmigrant alien."

Despite the requirement, the ATF found that Michigan CPLs have been and continue to be issued for certain people without determining whether the applicant is prohibited under federal law from owning or transporting a firearm.

"Specifically, ATF learned that CPLs were and continue to be issued to applicants who were likely prohibited due to a conviction for a misdemeanor crime of domestic violence, and to habitual marijuana users," the letter reads.

Despite marijuana being legal in Michigan, it is still a controlled substance under federal law, and those who use it are prohibited from owning or transporting a firearm.

Under this determination, a valid Michigan CPL is no longer an alternative to the NICS check, and all sales from federal firearm licensees to a non-licensee must go through NICS.