## Facts

- Pneumoconiosis is a respiratory disease caused by inhalation of mineral dusts; silicosis is one type caused by silicic-acid dust.
- In 1949, Japan enacted the Mine Safety Law, which gave the Minister of International Trade and Industry authority to issue and enforce mine-safety regulations.
- In 1950, the minister issued safety regulations that required special designation of silicic-acid dust areas and imposed stringent measures in those designated areas to reduce inhalation of silicic-acid dust.
- A government-linked study conducted from 1955 to 1957 showed that inhalation of mineral dust generally, not only silicic-acid dust, could cause pneumoconiosis.
- In 1960, the legislature enacted the Pneumoconiosis Law, which stressed governmental prevention and defined pneumoconiosis broadly to cover disease caused by mineral dusts other than silicic-acid dust.
- After 1960, the minister’s mine-safety regulations continued to provide only general, non-specific dust-safety procedures for ordinary coal-mine conditions, even though more stringent measures were already used in designated silicic-acid areas.
- The minister did not extend the more stringent dust-control approach broadly to other mineral-dust conditions in mines until 1986.
- During the intervening period, coal-mine workers in the Chikuho region (and, in some instances, their successors) alleged they were exposed to harmful dust and later developed pneumoconiosis.
- The workers sued the State of Japan under Article 1(1) of the National Compensation Law, alleging that the government’s long-term failure to timely enact and enforce adequate dust-control regulations was an unlawful omission that caused their injuries.
- The court of second instance ruled for the workers, reasoning that it was extremely unreasonable for the government not to revisit and strengthen the regulatory scheme for such a long period after enactment of the Pneumoconiosis Law.
- The government appealed to the Supreme Court of Japan.

## Issues

1. Whether the minister’s long-term failure to exercise regulatory authority to strengthen mine dust controls, despite knowledge of pneumoconiosis risks and available measures, can constitute an unlawful omission under Article 1(1) of the National Compensation Law.
2. What standard governs when regulatory non-exercise moves beyond permissible administrative discretion and becomes unlawful, and how causation may be shown in long-term exposure cases.

## Decision

- The Supreme Court held that a failure to exercise regulatory authority may qualify as an unlawful act under Article 1(1) of the National Compensation Law when the competent authority is able to recognize a concrete danger and the danger could be avoided or reduced by exercising the authority, yet the authority does not take appropriate action.
- The Court agreed, on the record described in the litigation, that the minister’s prolonged non-exercise of authority to implement effective dust controls after pneumoconiosis risks were known could satisfy the unlawfulness requirement for state liability.
- The Court indicated that causation in this setting may be found where the omission materially increased the risk of pneumoconiosis and the disease in fact occurred among workers subjected to the hazardous conditions, while allowing limits based on timing and the portion of harm attributable to the period of unlawful inaction.
- The Supreme Court’s disposition left room for further case-specific determination of the scope of compensable harm, including limits tied to when the duty to act arose and the relation between the omission and each plaintiff’s condition.

## Legal Principles

- Under Article 1(1) of the National Compensation Law, an omission by an administrative authority can be unlawful when the authority could recognize a concrete, serious danger to individuals and could prevent or reduce that danger through the statutory powers available, but fails to take suitable measures.
- Administrative discretion in rulemaking and enforcement is not unlimited; extended non-action in the face of known health risks and available countermeasures may exceed the range of lawful discretion.
- In long-term occupational disease cases, causation need not be proven only through direct, individualized proof of a single source; it may be established where the unlawful omission significantly increased the risk of the injury that occurred, subject to reasonable limits.
- Any state liability for regulatory non-action is confined to harm attributable to the period after the government’s duty to act arose and to the extent the omission can be connected to the injury claimed.

## Conclusion

Japan v. Yamamoto holds that the State may be liable under the National Compensation Law for a prolonged failure to strengthen and apply mine dust controls once pneumoconiosis risks were sufficiently known and preventable through existing regulatory powers, and that causation may be recognized where the omission materially increased the risk of the disease that later developed, with damages limited to harm tied to the period of unlawful inaction.


Japan v. Yamamoto, Case 2001 (Ju) No. 1760, 58 Minshū 1032 (2004)