This is what I found:
How do you buy rifles and/or shotguns, including bb, pellet, and black powder rifles?
It is the responsibility of the seller of the rifles and/or shotguns, including bb, pellet, and black powder rifles to ascertain that the buyer has a valid Firearms Purchaser Identification Card plus one additional form of photo identification and completes a Certificate of Eligibility for each firearm. The information contained on the Firearms Purchaser Identification Card must match the identification of the transferor to be valid. A Certificate of Eligibility can be obtained at any licensed firearms dealer, or this web site. *All firearms transactions must be completed at a State licensed retail firearms dealer with the exemption of transactions between a) members of an immediate family b) law enforcement officers c) collectors in possession of a valid Collector of Curios and Relics License issued by the Bureau of Alcohol, Tobacco, Firearms and Explosives. (See N.J.S.A. 2C:58-3 for further information)