not technically but some FFLs won't accept from non FFL holders.
only gun dealers can use usps and fedex/ups require overnight shipment of firearms, which is why most people ship from FFLs (to save the shipping cost)
My cousin has a number of guns and high cap mags he needs too get out of CA soon. He found out to day he has prostate and bone cancer and he said CA aint keeping his guns and mags. CA law says his older guns and high cap mags can not be sold, given away are passed on if he dies what a shitty law