Then I guess lawmakers can. After a Brazilian model died of an anorexia-related infection (she was a "svelt" 88 pounds) several European countries, now including France have stepped up to keep the media accountable (sort of).
The law would make it illegal to incite people to "excessively" deprive themselves of food, and would apply to websites, magazines, and advertisements. Now obviously they're targeting those websites for "annies" and magazines/advertisers who use concentration-camp thin models and have articles about starving yourself. This is all excellent on the part of the models' health: if people aren't hiring models that have so few muscles they can't even hold themselves up because their bodies have consumed them in place of actual food, then the models will gain some weight and be less likely to starve themselves to death. This is also good for getting rid of those disgusting websites that help girls learn how to hide their anorexia and support eachother in it.
What this won't be so good for is helping normal-sized, non-anorexic girls have better body images (which apparently is part of the goal of the legislation). Obviously they aren't going to be slapping fines on Elle or Cosmo for having size 2 models, as it would be tricky to make the case that they are inciting people to try to be "excessively" thin. However, if you ask me, it's the size 2 models that are causing all the obsessive dieting and body-hating on the part of 95% of women. No one looks at a skin-and-bones model and says "man, why can't my body look like that?" (or at least very few people do). It's the thin-yet-evenly-proportioned-probably-has-at-least-some-food-in-the-very-flat-belly-could-seem-attainable-if-I-stopped-eating-chocolate-except-for-the-fact-that-it's-probably-all-genetic-and-I-was-cursed-from-birth-but-I-can-still-loath-myself-every-time-I-eat-junk-food-type models that destroy an average woman's self esteem and makes her obsess over calories and exercise and guilt when she's really quite beautiful already.
Can you imagine if they made a law where models actually had to be normal sized (and by that I mean at least a size 6, which is what models used to have to be only 5 years ago and THAT was considered a little overly thin)? I don't fully agree with measures like that, but just think about it....