California Bill Seeks to Regulate Homemade Guns A state lawmaker proposed Monday that California extend its requirement that gun buyers undergo background checks and register their weapons to anyone who assembles a firearm in their home. The legislation by state Sen. Kevin de Leon is part of a growing effort across the country to pre-empt the spread of undetectable guns that can be made using 3-D printers. His bill also would apply to anyone who buys parts that can be assembled into a gun. De Leon said he is trying to address a twin threat from what he called "ghost guns" - plastic guns that can slip through metal detectors and unregistered weapons that can fall into the hands of people who are legally prohibited from owning firearms under state law. "Currently, no one knows they exist until after a crime has been committed," said de Leon, a leading candidate to take over as Senate leader next year. That was the case for John Zawahri, who assembled his own military-style assault rifle and killed five people in Santa Monica in a June rampage even after he was barred from legally buying a gun in California because of mental health issues. The bill by De Leon, a Democrat from Los Angeles, goes further than the federal government, which last month renewed for 10 years an existing ban on plastic firearms that can evade metal detectors and X-ray machines. His bill, SB808, would allow the manufacture or assembly of homemade weapons, but require the makers to first apply to the state Department of Justice for a serial number that would be given only after the applicants undergo a background check. The number would have to be engraved on or otherwise permanently attached to the weapon within one day of its manufacture. He plans to amend the bill to also require that the guns contain permanent pieces of metal that could be detected by X-ray machines and metal detectors, a proposal that was blocked in the federal legislation. Some plastic guns currently comply with the federal law by including a metal piece that can be removed, which potentially would allow them to be slipped through security screeners at airports, courthouses, schools and elsewhere. The National Rifle Association did not oppose the 10-year extension of the federal plastic firearms ban. But spokeswoman Catherine Mortensen said the organization opposes any expansion of the law at either the federal or state level. Currently available technology allows consumers to download a gun's design plans to a computer and then build it on a three-dimensional printer with no background checks or other safeguards. Lawmakers in New Jersey and New York have introduced legislation that would ban the possession of weapons made using 3-D printers, said National Conference of State Legislatures policy specialist Jon Griffin. However, while there had been talk by federal lawmakers and some state legislators of trying to restrict the posting of weapons plans on the Internet, Griffin said he knows of no such legislation being introduced and said it would likely run into free speech protections. Nick Wilcox, representing the Brady Campaign to Prevent Gun Violence, said de Leon's bill is particularly significant because as of Jan. 1, those buying rifles and shotguns in California are required to undergo the same registration and background checks as are required of those buying handguns. California is also the only state that cross-checks five computerized databases to find people who bought firearms but are not permitted to own them.