Children inhabit a complex social world in which they must learn to navigate and understand the various rules used to coordinate decisions and behavior between themselves and others. Although people commonly think about rules as being either categorically fair or unfair, established rules can be highly context-dependent in how they are used. In this dissertation, I demonstrate that children are flexible and sophisticated reasoners about the use of impartial decision rules – both in determining when rules are fair to use, but also in determining that fair rules themselves can be utilized in highly unfair ways. In Chapter 1, I explore two very canonically fair rules studied within the resource distribution literature: merit and equality. I show that children evaluate these rules as unfair if they are applied in a morally inconsistent way to benefit the self. Importantly, I find that children do not have a broadly negative view of inconsistent rule use, but that it is specifically morally inconsistent rule use that is negative: although they believe that inconsistently using rules to benefit the self is bad, they do not think that inconsistently using rules to benefit others is bad. Next in Chapters 2 & 3, I explore a novel and important decision-making rule that has been underexplored in young children’s thinking but undergirds much of adult decision-making today: going with majority rules. In Chapter 2, I establish that children understand the use of majority rules and they use it across group decision-making contexts, even preferring it to another procedure that is viewed as very fair (coin flip). I further demonstrate that children are highly nuanced in how they evaluate majority rules voting. They understand that majority rules should be used for group decisions but not for decisions on behalf of individuals, and that they discern between types of claims that can be voted on (e.g., it is totally appropriate for preference decisions, but should not be to decide what is true or moral). Finally, in Chapter 3, I combine insights from the first two chapters to demonstrate that, although children believe that majority rules is fair as a decision-procedure for groups, they even attend to who is voting and benefiting from the decision rule—when those voting against a policy are the ones being disproportionately disadvantaged by it, it is seen as less fair than if they were in favor. Altogether, these results demonstrate a nuance in how children think about, and reason about complex impartial rules in the social world.