Constitutional Foundations

The legal scrutiny of gerrymandering begins with the U.S. Constitution, which establishes the principles for representative democracy. The Equal Protection Clause of the Fourteenth Amendment is a primary weapon against districts that intentionally dilute the voting strength of racial or ethnic minorities. The landmark cases Baker v. Carr (1962) and Reynolds v. Sims (1964) established the “one person, one vote” doctrine, requiring electoral districts to be roughly equal in population. While these cases addressed malapportionment—districts with vastly unequal populations—they opened the door for courts to hear challenges based on unfair district shapes and partisan bias.

Courts have consistently held that districting plans must not be drawn with discriminatory intent or produce a discriminatory effect. The First Amendment’s freedom of association also comes into play when partisan gerrymandering is alleged to penalize voters for their political affiliation. Together, these constitutional provisions form the bedrock for nearly every gerrymandering lawsuit filed in federal court.

Key Federal Laws

Beyond the Constitution, federal statutes provide additional guardrails. The most prominent is the Voting Rights Act of 1965 (VRA), particularly Section 2, which prohibits any voting practice or procedure that results in the denial or abridgment of the right to vote on account of race, color, or language minority status. Plaintiffs can challenge redistricting plans under Section 2 without proving discriminatory intent—only a discriminatory effect is required.

Before the Supreme Court’s 2013 decision in Shelby County v. Holder, Section 5 of the VRA required certain states and jurisdictions with a history of racial discrimination to obtain federal “preclearance” before changing their voting laws or district maps. The ruling effectively nullified that coverage formula, making it easier for those states to enact maps without prior federal review. This shift has led to an increase in litigation under Section 2 and state-level constitutional challenges.

Other federal laws, such as the Uniformed and Overseas Citizens Absentee Voting Act (UOCAVA) and the National Voter Registration Act (NVRA), indirectly affect district drawing by ensuring eligible voters are registered and can cast ballots, but the VRA remains the central federal tool for combating racial gerrymandering.

Landmark Supreme Court Decisions

Racial Gerrymandering

The Supreme Court has drawn a clear line against racial gerrymandering. In Shaw v. Reno (1993), the Court held that district boundaries drawn predominantly on the basis of race, even for the benign purpose of increasing minority representation, can violate the Equal Protection Clause if they are “bizarrely shaped” and cannot be explained on grounds other than race. Later cases like Miller v. Johnson (1995) refined the test: plaintiffs must show that race was the “predominant factor” in drawing district lines, and that the state failed to consider traditional redistricting principles (such as compactness, contiguity, and respect for political subdivisions). The Court has since struck down districts in North Carolina, Virginia, and Texas under this standard.

Partisan Gerrymandering

Partisan gerrymandering—drawing districts to advantage one political party—has proven far more difficult to challenge in federal court. The Supreme Court wrestled with the issue for decades. In Vieth v. Jubelirer (2004), a plurality of justices concluded that partisan gerrymandering claims were nonjusticiable because no manageable judicial standard existed. Justice Anthony Kennedy, concurring, left open the possibility that a workable standard might emerge in the future.

That opportunity came and went in Gill v. Whitford (2018), a challenge to Wisconsin’s state assembly map. The plaintiffs offered a new metric—the efficiency gap—to measure partisan bias. But the Court sidestepped the merits, ruling instead that the plaintiffs lacked standing to bring a statewide claim. Then, in Rucho v. Common Cause (2019), the Court held definitively that partisan gerrymandering claims present a political question beyond the reach of federal courts. Chief Justice John Roberts, writing for the 5–4 majority, stated that “partisan gerrymandering claims are not justiciable because they involve political considerations that are not susceptible to judicial resolution.” The decision effectively closed the federal courthouse door to plaintiffs seeking relief from extreme partisan maps, leaving regulation to state legislatures, state courts, and ballot initiatives.

Though federal courts can no longer hear partisan gerrymandering claims, they continue to analyze racial gerrymandering claims using a two-pronged approach: intent and effect. Under the predominant factor test established in Miller, a plaintiff must first show that race was the legislature’s predominant consideration. Courts examine evidence such as legislators’ statements, use of racial data, and the map’s departure from traditional districting principles. If that threshold is met, the burden shifts to the state to prove that the district would have been drawn the same way for legitimate, race-neutral reasons.

In state courts, however, partisan gerrymandering claims can proceed under state constitutions. Many state constitutions contain “free and fair elections” clauses, equal protection guarantees, or requirements that districts be “compact and contiguous.” States like Pennsylvania, North Carolina, and Ohio have seen successful state-level challenges striking down maps for extreme partisan bias. These cases rely on different tests—such as the “intent and effect” test used by Pennsylvania’s Supreme Court—rather than a single federal standard.

State-Level Responses and Reforms

With federal remedy all but eliminated for partisan gerrymandering, states have become the primary battleground for reform. The most significant innovation is the creation of independent redistricting commissions (IRCs). These bodies, composed of citizens or bipartisan experts, draw district lines without direct input from elected officials. States like California, Arizona, Michigan, Colorado, and Washington have adopted some form of IRC, often through ballot initiatives. Research shows that maps drawn by IRCs tend to be more competitive and less biased than those drawn by legislatures.

Other states have enacted statutory or constitutional amendments that impose stricter criteria for redistricting. For example, Florida’s Fair Districts Amendments (2010) prohibited drawing districts with the intent to favor or disfavor a political party or incumbent. The Florida Supreme Court has twice struck down the state’s congressional map for violating these standards. Similarly, Ohio voters established a redistricting commission with constitutional rules designed to produce maps that are “proportional and partisan-neutral” unless a supermajority of the commission agrees otherwise.

Litigation in state courts continues to be a powerful check. In 2022, the North Carolina Supreme Court (under a Democratic majority) struck down the state’s legislative and congressional maps as extreme partisan gerrymanders, relying on the state constitution’s free-elections clause. That decision was later reversed by a newly seated Republican majority in 2023, illustrating the volatility of state judicial remedies and the importance of judicial selection processes.

At the local level, some municipalities have experimented with ranked-choice voting or multi-member districts to reduce the impact of gerrymandering. While not a direct legal challenge to district boundaries, these alternative systems can make gerrymandering less effective by ensuring that winners earn a broader mandate.

Technical and Evidentiary Challenges

Proving gerrymandering in court requires sophisticated evidence. Plaintiffs often rely on geographic information systems (GIS) to show irregular shapes, computational simulations to demonstrate that a map is an outlier compared to thousands of neutral alternatives, and statistical measures like the efficiency gap, mean-median difference, and partisan bias. The efficiency gap, developed by law professor Nicholas Stephanopoulos and political scientist Eric McGhee, calculates the difference in “wasted” votes between the two parties—votes cast for a losing candidate or for a winning candidate beyond what they needed to win. While the Supreme Court did not adopt a specific test in Rucho, these metrics remain crucial in state court litigation and in public debate.

Expert testimony from political scientists and statisticians is standard, and courts have become more comfortable with quantitative evidence. However, the lack of a single accepted standard across jurisdictions means that the same map could survive a challenge in one state court and be struck down in another, depending on the legal framework applied.

Current Litigation and Future Outlook

As of 2025, several high-profile gerrymandering cases are pending in state courts. Alabama’s congressional map is under renewed scrutiny after the Supreme Court’s 2023 decision in Allen v. Milligan, which held that Alabama’s map likely violated Section 2 of the VRA by diluting Black voting strength. The Court, in a surprising 5–4 ruling, rejected Alabama’s argument that the VRA requires voting districts to be drawn on a colorblind basis and reaffirmed that race-conscious districting can be necessary to comply with the law. That decision has implications for other states with similar demographic patterns, including Louisiana, Georgia, and South Carolina.

Technology also poses new challenges. The increasing availability of fine-grained voter data and powerful redistricting software allows mapmakers to gerrymander with surgical precision. “Hijacking” and “cracking” techniques can be applied at the precinct level, making detection harder. In response, some advocates call for algorithmic or automatic redistricting to remove human bias, though such approaches raise their own constitutional and practical questions.

Legislative reform at the federal level remains stalled. The For the People Act (H.R. 1) passed the House in 2021 but failed in the Senate. It would have required all states to use independent commissions for congressional redistricting, among other measures. With divided government, prospects for nationwide reform are dim. Instead, the locus of activity will remain in state capitals, ballot initiatives, and state courts.

Finally, the composition of the U.S. Supreme Court matters. With a 6–3 conservative majority, the Court is unlikely to reverse Rucho anytime soon. However, the Court’s willingness to police racial gerrymandering and Section 2 claims, as seen in Allen v. Milligan, shows that the justices are not uniformly hostile to voting-rights litigation. The legal landscape remains dynamic, with new cases and procedural innovations emerging each election cycle.

For those seeking to understand the legal side of gerrymandering, the key takeaway is that remedies depend heavily on the type of gerrymandering alleged (racial or partisan), the venue (federal or state court), and the specific statutes and constitutional provisions at issue. While federal courts have largely closed the door to partisan claims, state courts and citizen-led reforms offer meaningful avenues for challenging unfair maps. As redistricting technology advances and political polarization deepens, the battle over how we draw the lines will only intensify.

For further reading, consult the Brennan Center for Justice’s comprehensive resources on redistricting, the SCOTUSblog for case updates, and the Congressional Research Service report on redistricting law.