Senator Kevin de Deon holds up untraceable AR-15 pattern rifles that were confiscated by Department of Justice after being used in crimes during a news conference on Monday, Jan. 13, 2014. 

A Senate Democrat wants to ban the sale of "ghost guns" in California.

Kevin de Leon of Los Angeles says he'll introduce a measure to outlaw the sale and manufacture of homemade firearms, weapons that are untraceable and don't show up on metal detectors.

"They are being produced without serial numbers or records of sale. No one knows they exist until after a crime has been committed," de Leon said. 

He says he's particularly concerned with online "how-to's" and the invention of 3D printers that can create plastic guns. The measure would require that anything self-assembled weapon contain permanent pieces of metal and be registered with the Department of Justice.