Tokyo, Oct. 8 (Jiji Press)–Japan’s Supreme Court is expected to issue a unified ruling within this year over lawsuits demanding that the results of the 2025 election for the Senate, the upper chamber of the Diet, the country’s parliament, be invalidated due to large vote-value gaps. Final arguments over the case were made at the top court’s Grand Bench, presided over by Supreme Court Chief Justice Yukihiko Imasaki, on Wednesday. The maximum vote-value disparity came to 3.13 times in the July 2025 election for the Senate, formerly known as the House of Councillors. The plaintiffs, two groups of lawyers, argued that the outcomes of the parliamentary election should be nullified because the massive gap violated the Constitution in terms of the equality of the value of votes. The lawyer groups filed a total of 16 lawsuits with the nation’s 14 high courts and high court branches. Eleven of the 16 rulings found that the triennial Senate election was conducted in a state of unconstitutionality, while the other five rulings said that poll was constitutional. None of the high courts or high court branches ruled the election unconstitutional or annulled the election results. The Supreme Court ruled in 2023 that the 2022 election for the upper chamber, which was held under the same framework as that for the 2025 poll, was constitutional in terms of vote-value gaps. The maximum disparity stood at 3.03 times in the 2023 election. At the time, the top court also said, “Legislative measures that can gain broad public understanding, including a fundamental review of the election system, are required.” In Wednesday’s final arguments, one of the two lawyer groups, led by Michihiko Misao, said that the Diet has neglected to make further law revisions although electoral district mergers, introduced from the 2016 election for the upper chamber, are effective in narrowing vote-value disparities. The other group, led by Hidetoshi Masunaga, argued that vote-value gaps expanded despite the Supreme Court pointing out in the 2023 ruling that rectifying the situation was a pressing challenge. The group called on the Supreme Court to rule the 2025 poll unconstitutional and invalidate the results of the election. Election boards, defendants in the lawsuits, rebutted by arguing that the Diet continues discussions on measures to further correct the situation after the election. Two pairs of sparsely populated neighboring prefectural constituencies in western Japan–Tottori and Shimane, and Tokushima and Kochi–were integrated starting with the 2016 election for the upper chamber. However, some in both the ruling and opposition parties are calling for the dissolution of the constituency mergers, citing low voter turnout. END [Copyright The Jiji Press, Ltd.]
