Exploiting a loophole, taking advantage of the ambiguity of language to do what someone says but not what they want, is a familiar facet of fable, law, and everyday life. Engaging with loopholes requires a nuanced understanding of goals, social ambiguity, and value alignment. Scientifically, the development of loopholes can help us better understand human communication, and design better human-AI interactions. However, cognitive research on this behavior remains scarce. A survey of parents reveals that loophole behavior is prevalent, frequent, and diverse in daily parent-child interactions, emerging around ages five to six. A further experiment shows that adults consider loophole behavior as less costly than non-compliance, and children increasingly differentiate loophole behavior from non-compliance from ages four to ten. We discuss the implications and limitations of the current work, together with a proposal for a formal framework for loophole behavior.