FUKUOKA — In another blow to a decades-old dam project on the Kawabe River in Kumamoto Prefecture, the Fukuoka High Court on Friday nullified a 1996 farm ministry decision that rejected complaints from local farmers over how water from the reservoir would be used.

The ruling effectively reverses a lower court decision and constitutes yet another setback to the 37-year-old controversial plan to build the dam.

The high court nullified part of a 1996 decision by the agriculture minister in rejecting the farmers’ complaints over the way changes were made to irrigation and other water-use schemes related to the dam.

The ruling calls into question one of the reasons why proponents justified the dam, which is being delayed due to opposition from a local fishery association. The government has had to carry over the budget for building the main part of the dam for four straight years.

Presiding Judge Katsumi Kobayashi said in handing down Friday’s ruling that the modified plans of two of the three projects did not have the required approval from local farmers and therefore are illegal.

Concerning two projects for drainage and land rearrangement, the high court found the government was unable to gain the required consent of two-thirds of some 4,000 farmers who would be affected.

In the case, 760 farmers appealed a September 2000 decision by the Kumamoto District Court, which had rejected their objections to changes in water projects, saying it did not see any flaws that made the modification process inappropriate.

The plaintiffs have expressed opposition to the dam itself but did not file for an injunction to stop the construction. They voiced objections to procedures taken by the Agriculture, Forestry and Fisheries Ministry in 1994 when it changed plans for the water-use projects by reducing their scope from the original schemes in 1984.

Chief Cabinet Secretary Yasuo Fukuda said later Friday that the government will carefully study the ruling before deciding on a response.

“We will decide (on whether to appeal) after the agriculture and other relevant ministries thoroughly discuss the matter,” the government’s top spokesman said.

Meanwhile, Naoto Kan, head of the Democratic Party of Japan, urged the government not to appeal the decision to the Supreme Court, stating that it should scratch the dam construction plan altogether.

In a written request addressed to Prime Minister Junichiro Koizumi, Kan said the government shoulders “grave responsibility” for promoting the project without the necessary consent of local farmers.

“There is no appropriate reason for the government to appeal, given the court ruling that the plan is illegal,” he said.

Kan handed the document to Fukuda at the Prime Minister’s Official Residence, as Koizumi was in Okinawa to attend a summit of Pacific island leaders.