The Fukuoka High Court on Monday rejected a suit demanding that the outcome of the July Upper House election be invalidated due to the disparity in the weight of votes.
The court said, however, that the maximum disparity of 3.08 times between the most and least populated constituencies in the July 10 election was "in a state of unconstitutionality."
The ruling is the 12th of its kind on 16 similar lawsuits filed with high courts nationwide by two groups of lawyers.
Four rulings have called the vote weight gap "constitutional," while seven have deemed them to be "in a state of constitutionality."
The election was held after the Diet took measures to address vote weight disparities. Two pairs of less-populated prefectures — Tottori and Shimane prefectures as well as Tokushima and Kochi prefectures — were combined into two electoral districts.
The vote weight disparity had narrowed from a maximum of 4.77 times seen in the previous Upper House election in 2013, which the Supreme Court had earlier judged to be in "a state of unconstitutionality," and urged the Diet to review the electoral districts.
A revised election law to rezone electoral districts was enacted in July 2015. But concerns remain that the rezoning will weaken the representation of rural areas in the Diet.