It was only a matter of time. Last month, the Center for Science in the Public Interest (CSPI) served McDonald’s with a notice of its intent to sue if the fast food giant continues to use toys to promote Happy Meals. (An “intent to sue” letter is a prerequisite to filing a lawsuit in some states.) The basis for the potential case is that using toys to market to small children is unfair and deceptive under the consumer protection laws in a number of states. According to CSPI’s letter, McDonald’s toy promotions violate the laws of California, Massachusetts, New Jersey, Texas, and the District of Columbia.

CSPI’s litigation director Stephen Gardner explained in a statement that “McDonald’s is the stranger in the playground handing out candy to our children. McDonald’s use of toys undercuts parental authority and exploits young children’s developmental immaturity.”

The letter more specifically describes the basis for the case:

McDonald’s practices are predatory and wrong. They are also illegal, because marketing to kids under eight is (1) inherently deceptive, because young kids are not developmentally advanced enough to understand the persuasive intent of marketing; and (2) unfair to parents, because marketing to children undermines parental authority and interferes with their ability to raise healthy children.

This is important because CSPI is saying that McDonald’s practices are both deceptive to children and unfair to parents, the latter to deflect the argument that it’s really all the parents’ fault. For that perspective, CSPI’s press release quotes Sheila Nesbitt of Minnesota, a parent of a six-year-old boy and a three-year-old girl:

McDonald’s makes my job as a parent more difficult. They market cheap toys that appeal to kids and it works. My kids always want to go to McDonald’s because of the toys. I try my best to educate my kids about healthy eating but it’s hard when I am competing against the allure of a new Shrek toy.