If the person in the photos ia a minor, then this would constitute possession
and distribution of child pornography. These are federal offenses that can put a person in prison for many years.
It's a more difficult situation to analyze if the person in the pictures is an adult. If so, it's much more difficult to say whether the actions were illegal. Any analysis would include whether the pictures were obtained with the consent of the person in the pictures. If the person in the pictures had knowledge and gave consent for the pictures to be taken and kept, there is an argument that the "owner" could do whatever he wanted with the pictures.
However, the analysis doesn't necessarily end there. Did the person ask for them back? Did the person expressly state that they could NOT be distributed? Is the person using them to harass the other person? If the answer to any of these questions is yes, then law enforcement MAY be willing to get involved. If they will not investigate, the person would still have the ability to get a restraining order (RO). The RO would prohibit the person from harassing the person in the pictures and/or distributing the pictures any further.
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