Most of the scholarship on private enforcement, in which individual citizens sue to enforce legal statutes, has focused on federal-level laws. In new research, Jeffrey Xia, Diego A. Zambrano, Neel Guha, and Austin Peters show how expansive and messy state-level private enforcement statutes are, and explain why previous theories on private enforcement do not explain the dynamic among the states. They conclude that research on state-level private enforcement demands much more attention than previously provided.


One of the most interesting and unique features of the United States legal system is also one of the most puzzling: unlike most countries, the U.S. relies primarily on private litigants to enforce its most important statutes. Whenever the federal government faces demands to solve a societal problem—environmental, economic, or otherwise—Congress typically responds by enacting a statute that gives private plaintiffs the right to sue alongside public enforcement. At the federal level, we do this across the board: civil rights, antitrust, environmental law, employment, etc. In many cases, Congress does not merely create a private right of action; it also pairs the right with additional incentives like fee shifting, treble damages, and class actions. In turn, private parties eagerly employ these rights, filing the vast majority of antitrust, employment, and environmental law claims. Nowhere else in the world do we see this degree of reliance on private litigation.

Given the significance of landmark legislation like the 1963 Clean Air Act and 1964 Civil Rights Act, it is no surprise that existing scholarship has focused exclusively on federal private rights of action. But the U.S. is a federal country, and across the fifty states there are fifty state legislatures and fifty distinct bodies of state law. How these states legislate their own private rights of action provides a deeper understanding of the U.S. legal system and the politics behind state-legislated private rights of action. Yet, prior to our work, nobody had systematically studied private enforcement at the state level. In a recent paper, “Private Enforcement in the States,” we analyzed all state statutory codes from 2003-2020 and found a world of private rights even more sprawling than the federal system. Sean Farhang, whose research has defined the study of private enforcement at the federal level, identified around 300 such clauses at the federal level. A conservative estimate pegs the number of private rights of actions provisions in state law at 3,500. The most liberal estimate calculates the number of private rights at around 10,000. These provisions cover everything from antitrust and employment to privacy and police violations and waste disposal.

Our findings show that state private enforcement is large, significant, and maybe even a bit chaotic. From a descriptive standpoint, some state statutes parallel federal private rights, but most diverge drastically. Farhang posited that Congress adopts private enforcement when the executive is controlled by the other political party, with the goal of insulating enforcement power from an ideologically distant executive. We find that this “separation of powers” theory, although robust at the federal level, does not explain the evolution of private rights of action at the state level. Our work opens up a previously unexplored world of state private enforcement for future study.

Parallels and Differences Between State and Federal Private Rights of Action

Some state private enforcement provisions mirror federal provisions in substance and structure. Take, for instance, the New Jersey Environmental Rights Act (NJERA), which allows any individual to sue to enforce environmental regulations. Like the federal equivalent, the statute’s legislative history suggests it was the product of thoughtful calculation about the importance of complementing public enforcement with private claims.

However, state private enforcement differs from federal enforcement in a variety of unexpected ways. To begin, states use private claims in disparate and niche areas under the traditional purview of state lawmaking power, including private rights of action in veterinary care, pet services, and grave digging. In addition, states tinker with their private rights provisions to a much greater degree than their federal counterpart. Most federal private rights of action have endured in their original form. For example, the core private enforcement provision in the Clayton Act has remained largely untouched since its passage. Not so in the states. In our research, we find that states frequently tinker with their private rights provisions, occasionally shoehorning private rights into already-existing legislation and sometimes even eliminating provisions altogether.

Consider a Mississippi provision which included a private right allowing “[a]ny person whose confidential record” of driving under the influence to sue when the record “has been disclosed.” In 2012, a Mississippi court considered an appeal invoking parts of the same provision regarding nonadjudication of DUI offenses for minors. The private right was not invoked, was not at issue, and its validity was not challenged. However, shortly afterward and seemingly in response to the court decision, the Mississippi legislature made substantial amendments to the statute and eliminated the private right. Our conclusion is that the private right vanished without much legislative debate and any press coverage. As far as we can tell, this type of abrogation—swift and silent—has never happened in federal legislation. However, we find similar spontaneous changes to private enforcement in other states.

Theories of State Private Enforcement

At the federal level, most scholarship has centered on Sean Farhang’s “separation of powers” theory. As previously mentioned, this theory posits that Congress is more likely to adopt private enforcement legislation when the presidency belongs to the other party, as enforcement agencies, such as the Department of Justice Antitrust Division are generally under the purview of the president. Yet, while the “separation of powers” theory has robust explanatory power at the federal level, it does not appear to explain patterns of private enforcement in the states. Whether looking at the raw data or regression analyses, we find no correlation between divided government and the adoption of private enforcement provisions. 

There are several possible reasons why theories of private enforcement at the federal level fail to explain the dynamics of private enforcement at the state level. One explanation is that enforcement power at the state level is often divided between governors and independently elected attorneys general, making it more difficult for state legislatures to predict whether executive branch enforcement will be weak or strong.

Another theory posits that states are more willing to copy private enforcement laws from either other states or from “model laws,” a dynamic that is absent at the federal level. Model laws are laws drafted by nation-wide, third-party organizations for potential enactment by state legislatures, and many come with private enforcement provisions. For example, the Uniform Law Commission drew up the model Athlete-Agents Act, which arms student athletes with a private right to sue other athletes or students violating the substantive provisions of the act. It was subsequently adopted by more than 40 states. Another popular model act, the Securities Act, was drafted in 2002 by the National Conference of Commissioners on Uniform State Laws and equips shareholders and investors with the right to recover damages for fraud and other securities violations. There are many other examples spanning controlled substances, animal welfare, and tele-health. In some cases, states adopt model laws simply because other states have done so as well. This reliance on model laws is absent at the federal level, underscoring how federal and state private enforcement co-exist within radically distinct institutional dynamics.

We also hypothesize that private enforcement may be more attractive for state legislatures because public enforcement may be weaker at the state level. Notably, the federal and state governments differ significantly in enforcement capacity, agency quality, and constitutional design. State agencies may be underfunded or under-resourced as a result of constrained state budgets. They are also generally less sophisticated relative to the federal administrative state, potentially because they enjoy a lower level of constitutional independence. Moreover, state public enforcement agencies are subject to a lower degree of citizen oversight; while federal agencies are constantly scrutinized by watchdogs of various political persuasion, states often lack similar grassroot sources of accountability.

At the end of the day, private enforcement is an even more crucial part of the American system than we initially thought. With the black box of state private enforcement now “open,” we sketch a future comparative research agenda to study the federal-state divergence and the broader intricacies of state private rights. The discoveries we present in this paper reaffirm the need to place private enforcement front and center in procedural scholarship and pedagogy. 

Articles represent the opinions of their writers, not necessarily those of the University of Chicago, the Booth School of Business, or its faculty.