How Constitutional Rights Matter explores whether constitutionalizing rights improves respect for those rights in practice. Drawing on global statistical analyses, case studies in Colombia, Myanmar, Poland, Russia, and Tunisia, and survey experiments in Turkey and the United States, this book advances three claims. First, enshrining rights in constitutions does not automatically ensure that those rights will be respected in practice. For rights to matter, rights violations need to be politically costly, which can happen when citizens mobilize against governments that encroach upon their rights. Successfully resisting the government, however, is no small feat for unconnected groups of citizens, and governments can often get away with constitutional rights violations. Second, some rights are more likely to be enforced than others. The reason is that some rights come with natural constituencies that are able to mobilize for their enforcement. This is the case for rights that are practiced by and within organizations, or “organizational rights,” such as the rights to religious freedom, unionize, and form political parties. Because religious groups, trade unions, and political parties are highly organized, they are well equipped to use the constitution to resist rights violations. Indeed, we find that these organizational rights are systematically associated with better practices. By contrast, rights that are practiced on an individual basis, such as free speech or the prohibition of torture, usually lack constituencies to enforce them, which makes it easier for governments to violate them. Third, even highly organized groups armed with the constitution face an uphill battle. Although such groups may be able to successfully resist repressive practices, they often can only delay governments that are truly dedicated to rights repression.