There is a lot of confusion about the regulation of so-called "large-capacity" magazines in California.

First, a note on terminology: I use the term "large-capacity" magazine because that is exactly the term used in California law. Federal law used to have a similar definition but that definition and set of restrictions ended with the sunset of the Federal assault weapons restrictions in September 2004. California law prohibits a surprisingly small amount of conduct regarding large-capacity magazines in Penal Code 12020 (a)(2):

Commencing January 1, 2000, manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, or lends, any large-capacity magazine.

It is very important to note that possession and use of a large-capacity magazine is not at all prohibited in California. The only prohibited acts are importing or manufacturing a large capacity magazine. Importing a large-capacity magazine includes things like driving one across the state border, flying in with it, or ordering it to be delivered from out-of-state. Importantly there is an exception for re-importing magazines that were legally possessed in the State of California prior to January 1, 2000 at Penal Code 12020 (b) (23):

The importation of a large-capacity magazine by a person who lawfully possessed the large-capacity magazine in the state prior to January 1, 2000, lawfully took it out of the state, and is returning to the state with the large-capacity magazine previously lawfully possessed in the state.

Subsections 19 to 33 have various other exceptions to the restrictions on large-capacity magazines for law enforcement and other state actors. It also includes an exemption for loaning large-capacity magazines at, for example, ranges as long as they stay within the "accessible vicinity."

Another important pair of issues are (1) the repair of legally possessed large-capacity magazines and (2) converting "large-capacity" magazines to become "10-rounders."

First, regarding the repair of large-capacity magazines, the California Department of Justice has opined in a letter dated November 10, 2005 that one can import any part of a large-capacity magazine to repair an exist­ing large-capacity magazine. This means that over time a large-capacity magazine can, in fact, have had all parts repaired or replaced. The basic rule of thumb is that one cannot end up with more large-capacity mag­azines than one started out with! The other important thing to know is that once a magazine is a large­ capacity magazine, there is no further "size limit." For example, a 20 AR round magazine can become a 30 round magazine with the replacement of the body and spring, while retaining the remaining parts. Just don't rebuild a 10-round magazine into a 20-or 30-round magazine.

Second, with the rise of the "Bullet Button" as a way to legally own what might otherwise be deemed an "assault weapon" (and its requirement that you only use 10-round magazines), many California gun owners are buying parts for "high-capacity" magazines and converting them to "10 rounders." (For more information about the "Bullet Button," see "GETTING AN AR OR AK STYLE RIFLE IN CALIFORNIA: It's Easier Than You Think!" published in the October 2009 issue of The Firing Line).

As long as you make "permanent" modifications so that a magazine can only hold 10 rounds of the ammunition, it is not a large-capacity magazine anymore. Generally, a simple block is not "permanent" enough, but a rivet through a body or a block that is held in by epoxy or similar methods (that would take more than a simple screwdriver to disassemble) appear to meet the permanence requirements.

A violation of Penal Code 12020 (a)(2) can be punished as either a misdemeanor or a felony under California law and is referred to in California legal circles as a "wobbler." The statute of limitations for a person to be charged with a wobbler is 3 years. One of the 58 DAs would have to have evidence that you manufactured or imported a magazine in the 36 months prior to charging you with a violation of 12020 (a)(2). Absent of watching you drive across the border, or having documentary proof of manufacturing, or being able to use a statement against you, enforcement of the restriction on large-capacity magazines is quite hard.

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If you've got old or worn out large-capacity magazines, you should feel completely free to repair those magazines at will. If you have a place outside of California where you can legally use large-capacity magazines, you can break down large-capacity magazines into parts before you return to California and simply store the parts as parts while you're back in California. With a little bit more understanding of California law, life as a gun owner can be even simpler. Keep watching too, as a post McDonald world may well make such point­less regulation invalid.

For more information:

CGF Wiki on Large-Capacity Magazines:
http://wiki.calgunsfoundation.org/index.php/Large-capacity_magazine_restrictions

CA DOJ Large-Capacity Magazine Letter:
http://www.hoffmang.com/firearms/DOJ-large-cap-magazines-­2005-11-10.pdf

About the author: Gene Hoffman is the Chairman of the Calguns Foundation, the co-inventor of the Bullet Button, a life member of the NRA, and a CRPA board member. When he's not using his C&R FFL, punching holes in paper, or punching holes in unconstitutional laws, he amuses two darling daughters and can sometimes be found shopping for his next boat.