Californians should be very cautious about purchasing things at gun shows outside California that might be illegal under either federal or California law.
Over the years the California Department of Justice Firearms Bureau (DOJ) has expanded its enforcement jurisdiction both inside and outside California. DOJ’s enforcement efforts now include attending out-of-state gun shows.
Undercover DOJ agents typically look for people arriving at a gun show outside of California in cars with California license plates. The DOJ agents then follow these individuals around the show, observe what they buy, and/or watch what the Californians bring back to their cars. If the Californian buys anything that is illegal to possess or import into California, DOJ often follows the person until they return to the state. These agents either pull the suspect over once they cross back into California, wait for the person to return home in California and then get a search warrant for their residence, or wait until the person stops in California on the drive home and then confront them.
At certain gun shows, some vendors are non-licensed sellers of firearms who are unfamiliar with California and federal laws. It is generally illegal for a Californian to acquire a firearm directly from an out-of-state seller/transferor, including one at an out of state gun show. In almost all situations, the firearm must be sent to a California federal firearm licensee (FFL) to complete the transfer. (This assumes that the California buyer does not have dual residency for the state in which the firearm is being acquired, does not possess a federal firearms license, that the firearm does not meet the definition of an “antique,” and the individual is not acquiring the firearm through bequest or intestate succession). A good rule of thumb is to never obtain a firearm directly from an out-of-state source. When in doubt, have the firearm sent to a California FFL to complete the transfer to you. Never fill out the Federal Transaction Record (commonly known as a 4473) using incorrect information (i.e. lying about your state of residence). Lying on a 4473 (a “lie and buy” case) is a serious crime.
Also, some types of firearms that are generally legal to possess in other states may nonetheless be illegal to possess in California. This includes “assault weapons” and “.50 BMG rifles.” The act of bringing these firearms into California carries with it serious state consequences (in addition to any federal charge you might face based on a possible illegal acquisition of the firearms at the gun show).
There are generally no federal restrictions on purchasing firearm related items or parts (with a notable exception being machinegun parts and firearm frames or receivers) out-of-state. But California law nonetheless prohibits possession and/or importation of a broader range of firearm related items and attachments than federal law restricts.
When acquiring items for firearms from out-of-state sources, remember in particular California’s restrictions on “large capacity magazines,” and “tracer” ammunition. Regardless of how one of these items is obtained out of state, Californians generally break the law by bringing these into California.
“Large capacity magazines”(LCM), are generally legal to possess, transfer, and transport throughout the United States. But with limited exceptions, LCMs are heavily regulated under California law and are illegal to bring into California.
Likewise with “tracer” ammunition. Tracer ammunition is generally legal to possess throughout the country. But tracer ammunition is considered a “destructive device” (DD) under California law. Those who possess a DD in California can be subject to felony prosecution.