If he has the copyright, he can control the works. Read the Copyright section on FreeAdvice.com.
One approach, that bears some element of risk, is just post it and if he finds out let him sue you and have a judge or jury decide.
If it was your understanding that you would own the images, and especialy if you told him you planned to post them on the Net, you may win. Or he may be bluffing.
But get a lawyer to counsel you locally before you do as if it comes to litigation, you'd best be prepared and fully understand the consequences. Obviously this is all about money -- he wants more (as photographers traditionally make their money by people ordering copies and NOT the taking of pictures. By getting him to name his price to relinquish his rights should limit the possible damages he may recover later.
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