§ 478.41 General.
(c) Each person seeking the privileges
of a collector licensed under this part shall
file an application, with the required fee
(see § 478.42), with ATF in accordance
with the instructions on the form (see
§ 478.44), and pursuant to § 478.47, receive
from the Chief, National Licensing
Center, the license covering the collection
of curios and relics. A separate license
may be obtained for each collection premises,
and such license shall, subject to the
provisions of the Act and other applicable
provisions of law, entitle the licensee to
transport, ship, receive, and acquire curios
and relics in interstate or foreign commerce,
and to make disposition of curios
and relics in interstate or foreign commerce,
to any other person licensed under
the provisions of this part, for the period
stated on the license. [emphasis added]
Looks to me like it's legal to buy C&R's out of state, but you can only sell out-of-state to another licensee.