Federal agents on Saturday executed a search warrant on a gun parts store in California, despite the store owner filing a temporary restraining order against their agency.

The Bureau of Alcohol, Tobacco, Firearms and Explosives had demanded that Dimitri Karras, the CEO of Ares Armor in National City, Calif., turn over the names of nearly 5,000 customers who had purchased an 80 percent lower receiver that reportedly failed to meet ATF specifications.

Karras, a former U.S. Marine, agreed to turn over the receivers, but refused to reveal the names of his customers. He then filed the restraining order.

Federal agents responded by obtaining an ex parte order, meaning they did it without Ares being present, giving them permission to execute a “lawful search.”

The ATF “is conducting a lawful criminal investigation of the illegal manufacture, distribution, sale, and possession of AR-15 variant lower receivers, which are considered firearms under the Firearms Control Act,” the federal agency said in its ex parte application, dated Friday.