Under the 1934 NFA, technically, individuals can possess full-auto if they apply for a license in advance of actually obtaining the unit. This is a Federal law, and some have argued that it is unconstitutional since requiring fees for the exercise of a Constitutional right is 'prior restraint' and therefore unconstitutional. However, if you live in California, you cannot own full-auto (even if you qualify under the NFA) because state laws forbid it. California law has therefore 'over-ridden' federal statute - probably that is also unconstitutional.
These laws stand partially because NO court in California nor the 9th Federal Circuit Court (as the cuurent makeup of those bodies is) will EVER rule in favor of the RKBA and against these laws and partially because nobody wants to 'do time' while waiting for their case to come up before the US SC.