A law firm is calling on the U.S. Marine Corps to reverse a decision denying a trademark license to Shields of Strength, a private business that produces military-themed dog tag replicas with Scripture on them.

The company has had to deny thousands of requests for the dog tags after a group's complaint last year. First Liberty Institute sent a letter to the Marine Corps Trademark Licensing Office Tuesday accusing it of discrimination for abruptly pulling the license.

GROUP CHALLENGES SPACE FORCE'S USE OF BIBLE IN SWEARING-IN CEREMONY

That came days after the Military Religious Freedom Foundation (MRFF) complained about Shields' partnership with the Department of Defense. The group said the federal agency "poisons the constitutionally mandated separation of Church and State" with the Shields of Strength.

Shields founder Kenny Vaughan has made more than 4 million of the faith-based dog tags to date, donating hundreds of thousands to the U.S. military, including Gold Star families. He was devastated when he found out about the military's quick turnaround.

“It’s frustrating that those who are fighting for our freedom can’t have a Shield simply because the military is afraid of an outside activist group,” Vaughan said in a statement. “I hope the Marine Corps reverses course and restores the ability of our brave military members to own a Shield of Strength.”

Mike Berry, chief of staff for First Liberty Institute, wrote in the letter to the Marine Corps trademark office that the branch has violated the Religious Freedom Restoration Act by sending a directive to Shields of Strength telling it to remove all biblical references from its Marine Corps-licensed products. Shields has been making the tags for the last 20 years.

“Events of the past several weeks make clear that our military personnel are constantly exposed to danger. And yet the MRFF seeks to deny them the freedom to wear Shields of Strength,” Berry said. “Denying our troops a source of inspiration, hope, and encouragement simply because it contains a religious message is an outrage."

CLICK HERE TO GET THE FOX NEWS APP

Berry, who served active duty in the Marine Corps for seven years, added: "The Marine Corps should tell the MRFF to support our troops, not punish them.”

In December, members of Congress, including Rep. Ralph Abraham, R-La., and Sen. Ted Cruz, R-Texas, called on the Defense Department to reverse the decision.