Reiwa 7 (Gyo-Ke) No. 2, Action to Invalidate Election Due to Vote Weight Disparity

Following the October 2024 House of Representatives election, a group of voters filed an administrative lawsuit with the Tokyo High Court to invalidate the election results, arguing that the maximum population disparity between single-seat constituencies had reached 2.06 times, violating the constitutional principle of equality (Article 14). The case was elevated to the Supreme Court as Reiwa 7 (Gyo-Ke) No. 2. The plaintiffs contended that the Diet had failed to rectify malapportionment despite repeated judicial warnings, thereby undermining the integrity of the democratic process. The state argued that ongoing redistricting efforts met the legislative duty. The Supreme Court Grand Bench heard the case to determine whether the disparity constituted an unconstitutional state requiring judicial invalidation of the election.

The Supreme Court Grand Bench ruled the disparity to be in an unconstitutional state, but declined to invalidate the election. It emphasized that the Diet had made substantial redistricting progress, and that immediate invalidation would severely disrupt governance while the time remaining for corrective legislation was still reasonable.

Whether the 2.06-fold vote weight disparity in the 2024 general election exceeded the constitutionally permissible limit under Article 14 (equality) and Article 44 (legislative discretion), and whether the election should be entirely invalidated as a remedy.

The ruling intensified public demand for a rigid apportionment formula, accelerating bipartisan discussions on adopting the Adams method for seat allocation. It also sparked renewed civil society campaigns for constitutional amendment proposals to codify stricter population equality standards, and heightened voter awareness of district boundary inequalities.