In all honesty, I have never had the opportunity to make this argument in court, but I would think they are like anything else accumulated during marriage - community property. In other words half hers and half yours. That being said, you have to be real careful what you do with them. You should not go around posting them online or something. You could get in some serious trouble.
When this issue arises around family photos, the solution is to make copies. In this case, I doubt that solves the problem in her eyes. I suggest you not turn this into an expensive court battle. Give her the photos.
I agree with my colleagues, above. The photographs, whether digital or print, were community property and should have been handled in the divorce. Separate from the right to possess, however, is the right to distribute - no matter who owns the photographs be aware that you can't publish or distribute them (even without compensation) unless the subject of the pictures (your ex-wife) has signed a release.
Best advice - give her the photos.
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