Colegrove v. Green

Illinois voters (plaintiffs) sued over the significant population disparities among the state's congressional districts, which had not been redrawn in four decades despite major population shifts, arguing the state's inaction violated the "one person, one vote" principle; Illinois argued that the Supreme Court's earlier decision in Giles v. Harris precluded equitable relief on political-question grounds.

Whether federal courts should decide inherently political questions.