This can be a touchy subject, although I have not had to test any of this issue in court, but here’s how I understand copyrights.
When you are an employee or under a work-for-hire contract, the client owns everything. This can be touchy because a lot of clients like mine put work-for-hire language in the small print on a purchase order, which, by excepting, you agree to, whether you sign it or not.
BUT, and this is a big but, if you are hired by verbal agreement, and no paperwork regarding rights is put forward or signed, the client has the right to use the material for the intended use, and that’s it. You own everything. No amount of dubbing, duping or turning over tapes makes a dent in your rights. You can re-sell the work, or put it up as stock, whatever. Course in this situation there may be other rights that need to be considered, like talent, location fees, releases etc., and whether or not you want to piss off your client, but the work is yours.
I’m not a lawyer, but I had in my ad days an Intelectual Property law firm for a client, and I checked these statements with another copyright lawyer I know.
Funny, but despite the law, I have never had a discussion or conflict about this with any clients, I guess the unwritten laws of trust apply pretty widely in our biz, but it’s good to know the facts just in case…