San Diego County jumped into California’s sprawling ghost gun fight this week, suing a 3-D printing filament manufacturer it says hocks material for homespun firearms in violation of state law.

Working with the Giffords Law Center, the county counsel sued manufacturer Polymaker, alleging the company made a “strategic business choice” to market and sell 3-D printer filament to Californians for the express purpose of building illegal weapons. The polymer filament is sold in spools that feed into 3-D printers, allowing the devices to form designs created by their owners.