Japan's top court on Monday turned down an appeal by Okinawa Prefecture against the central government's order, which will allow it to proceed with landfill work for the relocation of a key U.S. base within the southern island prefecture.

The Supreme Court's First Petty Bench has upheld the Fukuoka High Court's Naha branch ruling, confirming the central government's authority to instruct the local government to approve modifications to its plans aimed at reinforcement of soft ground at a designated construction site.

Photo taken in May 2023 shows the Henoko coastal district of Nago, Okinawa Prefecture, the site for the relocation of the U.S. Marine Corps Air Station Futenma. (Kyodo)  

Following the unanimous decision of the five justices, top government spokesman, Chief Cabinet Secretary Hirokazu Matsuno, told a press conference that he expects the prefecture to "swiftly act in accordance with the ruling."

"We were hoping for a fair and neutral ruling until the last moment. It is extremely regrettable," Okinawa Gov. Denny Tamaki said at a press conference in Naha.

The ruling paves the way for resuming the suspended work, even as Okinawa and the central government remain at odds over relocating U.S. Marine Corps Air Station Futenma in the residential district of Ginowan to the less densely populated Henoko coastal area in Nago.

In 1996, Tokyo and Washington agreed on a relocation plan that involved returning the land occupied by the airfield, and in 1999, Tokyo selected Henoko as the relocation site. However, residents in Okinawa, which hosts the majority of U.S. military facilities in Japan, continue to strongly oppose the relocation.

Okinawa Gov. Denny Tamaki attends a press conference after Japan's top court on Sept. 4, 2023, turned down an appeal by the local government against the state's order to advance landfill work for the relocation of a key U.S. base within the southern island prefecture. (Kyodo) ==Kyodo

In 2013, the prefectural government approved the landfill work to build a replacement facility in the Henoko area under the leadership of then Gov. Hirokazu Nakaima, but his successor Takeshi Onaga rescinded the approval in 2015.

The Supreme Court, however, ruled the retraction was unlawful, with the landfill work commencing in 2018.

After soft ground was discovered at the planned reclamation site, the Defense Ministry applied for the change of construction plans in April 2020, but Tamaki disapproved the request, citing a lack of research.

The infrastructure minister in April last year overrode the prefecture's disapproval and issued the correctional order to Okinawa to admit the modifications.

The Okinawan government sought to have the central government's decision and the correction order nullified in separate lawsuits filed with the Naha branch in August 2022, but the high court rejected the prefectural government's claims in both cases in March.

In the former case, the Supreme Court on Aug. 24 turned down the prefecture's nullification appeal, while on Monday, the same court upheld the legality of the central government's correction order, citing its compliance with the local autonomy law.

Related coverage:

Japan's top court nixes Okinawa bid to halt U.S. base landfill work

PM Kishida vows to relocate U.S. base in Okinawa despite local backlash