A court on Wednesday ruled July's Upper House election was in a "state of unconstitutionality" due to disparities in the weight of a single vote between urban and rural constituencies.
But the high court in Takamatsu, Kagawa Prefecture, turned down the plaintiffs' demand to nullify the election results in three electoral districts on the island of Shikoku.
The ruling was the first since two groups of lawyers filed a series of suits with 14 high courts and their branches across Japan following the July 21 House of Councilors election.
The maximum vote-value disparity of 3.08 seen in the previous 2016 Upper House election was reduced to 3.00, after the Diet passed legislation in 2018 to narrow such disparities by adding six seats to the chamber and re-drawing electoral districts.
In the July election, Miyagi Prefecture had the largest number of voters per candidate, while Fukui Prefecture had the fewest.
The plaintiffs have argued that the allocation of electoral districts was not fundamentally reviewed, and violated the Constitution's requirement for fair elections in terms of seats being proportional to the number of voters.
The defendants — the election boards of the three constituencies — have maintained that the disparity was "not an extremely unfair condition that infringes on the Constitution."
The Supreme Court has previously ruled that the 2010 and 2013 Upper House elections — in which the vote-value gap reached up to factors of 5.00 and 4.77, respectively — were held "in a state of unconstitutionality," and ordered the Diet to address the sharp imbalance.
But in 2017, the top court ruled that the 2016 Upper House election, held with a vote weight gap of up to 3.08, was "constitutional."