No matter how well-intentioned, regulation often has unintended consequences. A case in point is the Children’s Online Privacy Protection Act of 1998 (COPPA), a law that mandates certain online privacy protections for children under the age of 13. A new study documents how the law has encouraged many kids—often with the help of their parents—to lie about their ages online and evade age-based restrictions. The authors also conclude that COPPA “inadvertently undermines parents’ ability to make choices and protect their children’s data.”

It wasn’t supposed to work out this way. The goal of COPPA was to enhance parents’ involvement in their children’s online activities and better safeguard kids’ personal information online. COPPA is a complicated law, however, and its “parental consent” provisions have proven difficult to enforce...