Duplicity from the Trial Lawyers' Pocket
In Wisconsin, if you drive without a helmet and you are involved in an accident (for whatever reason), the person responsible for the accident cannot introduce evidence that he did not wear a helmet and thereby failed to reduce his own damages by taking reasonable precautions. Why? According to the Governor of Wisconsin, he would not want to penalize a motorcyclist who was acting within the law. (Apparently helmets are not required in Wisconsin). He would rather penalize the defendent, who had no choice whether the motorcyclist put on a helmet that day. See here for more.

In contrast, the same Governor of Wisconsin has refused to sign a bill that would bar lawsuits against restaurants based on the obesity of its patrons. Although the restaurants are also acting within the law when serving food, the Governor reasons that the courts can sort through it all. See here for more.

What do you think would happen if a restaurant declined to serve an obese person?

Its lose/lose for defendants in Wisconsin.