My response:
The question then becomes, why would you want to keep the negatives? Surely, the only person interested is the model, and the model is about ready to sue you.
Let me explain why I believe you're going to lose any potential lawsuit.
1. There was no written contract specifying rights of the parties. Because any contract is verbal (except for the receipt you gave her for her payment), this part will be a "he said / she said" and the court will not indulge this.
2. The customer is not a "public figure" or is not "newsworthy." The customer is a private citizen.
3. Without a written and signed authorization, you cannot display her likeness in your shop, or anywhere because you'd run afoul of privacy laws, and laws against use of someone's likeness for use in advertising (which is why you'd want to display the picture in your shop).
4. You have no common law copyright because you have never displayed the photos on your own, or for the purpose of copyright. If you did attempt that, see number 3 above.
5. Her argument would be that the deal did, in fact, include negatives "because they are only of me, and he acknowledged the fact that he can't use them for himself."
6. The negatives are not otherwise "artistic" in nature. They are of private citizens, and have no altruistic, or intrinsic interest except to the subject model. They are typical wedding pictures; nothing special.
7. The negatives would merely be collecting dust in your drawer because you can't use them in any commercial capacity.
8. She has paid a price to you, and since you cannot use the photos or negs for any commercial purpose without authorizations, the implication and the greater weight would be that in the absence of an agreement to the contrary, all benefits flowing from the taking of the photos, and ownership rights thereto because of payment to you, vest in the subject model of the photos.
9. I have scoured the Internet, and lo and behold, it appears that innumerable photographers do, in fact, include negatives in the purchase price, turning possession, custody and control of any such negatives over to the customer. She could use this as proof of "custom and practice."
Give her the negatives, and chock it up to experience. Now that you have a written contract that includes this subject, you shouldn't have ownership problems in the future.
IAAL.
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