TOKYO - Japan's Supreme Court ruled Wednesday that the up to 3.13-fold disparity in the weight of votes in the July 2025 Senate election was in a "state of unconstitutionality," but dismissed requests to nullify the results.
The top court said in the ruling that parliament's efforts to reduce vote disparities had "stalled," describing the 3.13-fold gap as "hard to ignore."
It was the court's first judgement that a Senate election was in a state of unconstitutionality since the country merged two pairs of less-populated prefectures into two constituencies for elections in 2016, in a bid to reduce the gap in the value of votes.
The court had ruled the vote disparities in the previous upper house elections in 2016, 2019 and 2022 constitutional.
Wednesday's decision over the results of the election on July 20 last year followed 16 rulings from the lower courts, with 11 finding the disparity was in a state of unconstitutionality and five deeming it constitutional.
In the election, the disparity in the weight of votes between the most and least populated constituencies widened to 3.13-fold from 3.03-fold in the previous election in 2022.
Groups of lawyers who filed the 16 lawsuits across the country claimed that the vote weight disparity in the 2025 upper house race violated the Constitution's requirement for fair elections, arguing that the parliament had not corrected the disparity before the election.
Election commissions across the country countered that the gap had widened only slightly.
Legal experts have said if a disparity is significant, a court will deem the election to be in a state of unconstitutionality and rule it to be unconstitutional if the Diet does not address the issue within a reasonable period.
The top court's previous finding of a "state of unconstitutionality" was for the 2013 election, which had a maximum 4.77-fold gap. It had also deemed the 5.00-fold disparity in the 2010 election to be in a state of unconstitutionality.
In a revision to the election law ahead of the 2016 election, Tottori and Shimane prefectures were merged into one constituency and Tokushima and Kochi into another.
The vote disparity was 3.08-fold in 2016 and 3.00-fold in 2019.
