Environmental citizen suits were founded on the belief that empowering organizations and individuals to take legal action would provide a backstop against lax federal or state programs. Working in conjunction with the system of cooperative federalism, citizen suits were designed to uphold minimum levels of environmental protection and to provide a restraint on so called "races to the bottom" in which states compete for economic development by relaxing environmental standards. To our knowledge, no one has considered whether the geographic distribution of citizen suits could have the opposite effect-namely, that it reinforces rather than mitigates disparities in the levels of environmental protection. Yet we observe this phenomenon in data spanning two presidential administrations: citizen suits are filed in a small number of states with strong public support for environmental policies and robust state programs-not in states where policies and enforcement lag.

The small number of citizen suits and skewed geographic distribution of cases revealed by our data upend the narratives of proponents and critics of citizen suits. Among environmentalists, citizen suits are lauded for their capacity to augment government enforcement and to compel lax or ideologically antagonistic administrations to take legally required action. For skeptics, citizen suits threaten the constitutional authority of federal agencies to implement the law and allow private organizations to exploit broad legislative mandates. Neither perspective is borne out by the observed patterns of litigation, which are dominated by "wholesale" litigation challenging major policies rather than "retail" litigation against private entities. In fact, retail litigation accounted for just 18 percent of the environmental citizen suits filed over 16 years.

Taking a broad view of citizen suits, we find that the different statutory regimes facilitate or impede citizen suits in predictable ways. Structural limits are evident in statutes, such as the Clean Water Act, that minimize the barriers to filing citizen suits, as well as those for which the barriers are highest, such as the Clean Air Act. These limits are also evident in plaintiffs' preference for procedural claims, which accounted for almost 40 percent of the citizen suits in our dataset. These findings demonstrate the importance of the practical and structural limits of citizen suits to identifying effective reforms. The Article proposes a series of recommendations, both within and outside of the federal government, designed to mitigate the inequitable distribution of citizen suits and the resource limits that so often limit access to them.