The issue at hand is copyright infringement. Because the pictures Hadid, Lopez, Kardashian (along with Justin Bieber, Ariana Grande, Jessica Simpson and scores of other stars) published were captured by photographers

The issue at hand is copyright infringement. Because the pictures Hadid, Lopez, Kardashian (along with Justin Bieber, Ariana Grande, Jessica Simpson and scores of other stars) published were captured by photographers who make their living off of selling said shots, they're not all that happy when stars share them with their followers for free, thus instantly devaluing their worth. And, no, it doesn't matter that the pictures are actually of the celebrity themselves. They don't own the actual image, provided it was captured in a public place.

"If you paint a portrait of a celebrity, that celebrity can't then take your canvas and do what he wants with it just because it's his or her image," Domenic Romano and Leah Norod, a managing partner and entertainment law associate at NYC-based Romano Law PLLC, point out to E! News. "The same is true of a photograph—there are two sets of rights, that of the subject and that of the creator."

So in order to use that image and avoid an infringement claim, explain the attorneys, "Celebrities should clear the usage with the photographer and pay them a fair sum that correlates with the proposed use." In other words, they should shell out the same licensing fee the photog would charge to a magazine or website that might want to publish it.