http://www.thehighroad.org/showpost.php?p=7693730&postcount=4
[1] Under federal law, any transfer (with a few, narrow exceptions, e. g., by bequest under a will) from a resident of one State to a resident of another must be through an FFL.
[2] In the case of handguns, it must be an FFL in the transferee's State of residence.
[3] In the case of long guns, it may be any FFL as long as (1) the long gun is legal in the transferee's State of residence; and (2) the transfer is in compliance with the laws of the State in which it takes place; and (3) the transfer complied with the law of the transferee's State of residence.
[4] In connection with the transfer of a long gun, some FFLs will not want to handle the transfer to a resident of another State, because they may be uncertain about the laws of that State. And if the transferee resides in some States (e. g., California), the laws of the State may be such that an out-of-state FFL will not be able to conduct a transfer that complies.
[5] This applies to all interstate transfers, whether a sale, a gift, a trade or anything else. There are no exceptions under the applicable federal laws for gifts, whether between relatives or otherwise, nor is there any exception for transactions between relatives.
[6] The relevant federal laws may be found at: 18 USC 922(a)(3); 18 USC 922(a)(5); and 18 USC 922(b)(3).