I've been considering trying to sell antler pens as well. I called the district office and was referred to to this code:
California Fish and Game Code Section 3039
Legal Research Home > California Laws > Fish and Game Code > California Fish and Game Code Section 3039
(a) Except as otherwise provided in this section and Sections
3087 and 4303, or any other provision of this code, or regulations
adopted pursuant thereto, it is unlawful to sell or purchase any
species of bird or mammal or part thereof found in the wild in
California.
(b) Products or handicraft items made from furbearing mammals and
nongame mammals, their carcass or parts thereof, lawfully taken under
the authority of a trapping license, may be purchased or sold at any
time.
(c) Shed antlers, or antlers taken from domestically reared
animals that have been manufactured into products or handicraft
items, or that have been cut into blocks or units which are to be
handcrafted or manufactured into those articles may be purchased or
sold at any time. However, complete antlers, whole heads with
antlers, antlers that are mounted for display, or antlers in velvet
may not be sold or purchased at any time, except as authorized by
Section 3087.
(d) Notwithstanding Section 3504, inedible parts of domestically
raised game birds may be sold or purchased at any time.
(e) Any person who illegally takes any bird or mammal for profit
or for personal gain by engaging in any activity authorized by this
section is subject to civil liability pursuant to Section 2582.
Hope this helps,
Cheers,
Rob