A high court on Thursday upheld a lower court ruling that found a prominent anti-U.S. military base activist in Okinawa guilty of several criminal offenses committed during protests in the island prefecture.

Hiroji Yamashiro, 66, a key figure in the movement against the relocation of the U.S. Marine Corps’ Air Station Futenma within Okinawa, was given a two-year jail term, suspended for three years, in March for obstructing base transfer work and other acts.

Yamashiro, who is the head of the Okinawa Peace Action Center, was seeking to overturn the Naha District Court ruling, but the Naha branch of the Fukuoka High Court rejected his appeal.

The criminal trial of Yamashiro caught public attention due to his monthslong detention by authorities that prompted human rights groups to voice criticism of what they considered his unnecessary confinement.

The March ruling found Yamashiro guilty of obstructing relocation work at U.S. Marine Corps’ Camp Schwab after he piled blocks at its gate in January 2016 and cut barbed wire at the site in October of the same year. He was also found guilty of injuring a local Japanese defense bureau official in August 2016 near a U.S. military training site in Higashi.

“I find the decision unfair. We will face the biggest challenge yet from tomorrow but won’t give up,” said Yamashiro at a gathering after the high court ruling, referring to landfill work that the Japanese government plans to start Friday in the coastal district of Henoko, in the city of Nago, where the new base will be constructed.

Yamashiro is considering an appeal.

During the trial at the high court, the defense team said Yamashiro should be acquitted of all charges aside from the property damage caused when he cut the barbed wire.

They said Yamashiro was merely “expressing his opposition under the freedom of expression guaranteed by the Constitution” when he piled blocks at the gate of Camp Schwab, and that applying the charge of obstruction of work would be unconstitutional.

But the high court rejected their claim.

“The blocks piled in front of the gate weighed about 20 tons in total. The construction work was unjustly disrupted beyond the scope of the freedom of expression,” presiding Judge Masamichi Okubo said.

Many residents of Okinawa, which hosts the bulk of U.S. military facilities in Japan, want the Futenma base that is located in a crowded residential area of Ginowan moved out of the prefecture altogether, rather than transferred to Henoko.

But Japan’s government under Prime Minister Shinzo Abe has maintained that the base relocation to Henoko is “the only solution” for removing the dangers posed by the base without undermining the deterrence provided by the Japan-U.S. security alliance.

The government plans to start full-fledged land reclamation work on Friday for the construction of the controversial replacement facility.