1. Introduction

Energy law governing advanced geothermal technologies in Japan concerns the legal framework for exploring, developing, operating, and decommissioning geothermal energy projects while protecting the environment, groundwater, hot springs (onsen), public safety, and the interests of local communities.

Japan is particularly significant in this field because it possesses substantial geothermal resources due to its volcanic geology. However, many promising geothermal areas are located in or near national parks, established hot-spring resorts, and environmentally sensitive landscapes. Consequently, geothermal regulation requires a balance between energy security, decarbonisation, technological innovation, tourism, and conservation.

Advanced geothermal technologies include:

Enhanced Geothermal Systems (EGS): techniques that improve underground permeability so heat can be extracted from hot rock.

Advanced geothermal drilling: directional drilling, deep-well drilling, and high-temperature drilling techniques.

Closed-loop geothermal systems: circulating working fluids through sealed underground pipes to extract heat without deliberately producing geothermal fluids from the reservoir.

Supercritical geothermal development: exploration of extremely hot, high-pressure underground resources.

Advanced reservoir monitoring: seismic monitoring, pressure measurement, geochemical analysis, and computer-based reservoir modelling.

Binary-cycle geothermal power generation: using geothermal heat to vaporise a secondary working fluid, allowing electricity generation from resources that may be unsuitable for conventional steam turbines.

The central legal issue is that Japan's traditional geothermal framework was largely developed around conventional geothermal wells and naturally occurring hot springs. New technologies may create different risks, so regulators must determine how existing laws apply to unfamiliar methods of drilling, fluid circulation, stimulation, and heat extraction.

Important legal distinction: Japan does not regulate all geothermal activities through a single comprehensive geothermal statute. The applicable rules are distributed across mining, environmental protection, hot-spring conservation, electricity regulation, land-use planning, water protection, and other legal regimes.

2. Main legislation governing geothermal technologies

Japan's geothermal legal framework is best understood as a combination of statutory requirements, administrative guidelines, local rules, and judicial principles.

Principal legal sources

These laws operate together. Compliance with one does not automatically establish compliance with the others.

2.1 Hot Springs Act (Onsen-hō)

The Hot Springs Act is one of the most important statutes for geothermal development. Its stated objectives include protecting hot springs, preventing accidents associated with combustible natural gas, and ensuring appropriate use of hot-spring resources.

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Section 3 — Permission to drill

A person intending to drill land for the purpose of causing a hot spring to emerge generally needs permission from the prefectural governor.

This requirement is particularly relevant to conventional geothermal projects because exploration and production wells may intersect underground hot-spring systems.

Section 4 — Assessment of drilling applications

The statutory framework governs the circumstances in which drilling permission may be granted. The applicant must satisfy the applicable legal conditions, and the authorities must consider relevant resource-protection concerns.

Sections 12–14 — Protection of hot springs and related controls

The Act contains provisions dealing with restrictions on extraction, changes affecting hot-spring resources, and related protective measures. The precise approval or notification requirement depends on the activity and applicable provision.

Sections 14-2 to 14-10 — Natural-gas extraction safety

These provisions address risks associated with combustible natural gas released during hot-spring extraction, including relevant permissions, safety measures, and emergency intervention.

Section 15 — Public bathing and drinking

Using hot-spring water for public bathing or drinking generally requires a separate permit. A geothermal electricity generation permit does not itself authorise commercial public bathing or drinking-water use.

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Application to advanced technologies

Consider an operator proposing to drill a deep geothermal well using directional drilling. The operator must establish whether the operation falls within the Hot Springs Act's drilling requirements. The legal analysis depends partly on the purpose of the drilling and whether the activity is intended to cause a legally defined hot spring to emerge.

A genuinely sealed closed-loop system may present a different statutory question from a production well that extracts hot water or steam. However, a developer should not assume that calling a project “closed-loop” exempts it from drilling, environmental, land-use, or electricity-safety rules.

2.2 Natural Parks Act, 1957

The Natural Parks Act is important because geothermal resources frequently occur in volcanic landscapes protected for their natural, scenic, ecological, or recreational value.

The Act provides a system of special and ordinary zones within national and quasi-national parks. Depending on the zone and activity, development may require permission, notification, or compliance with restrictions governing structures, land alteration, vegetation removal, and other activities.

The Ministry of the Environment has issued geothermal-development guidance addressing how projects should be considered in natural parks. The guidance has been adjusted over time to facilitate appropriate development while protecting conservation objectives.

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For an advanced geothermal project, the assessment may include:

Whether a drilling pad, access road, pipeline, or generating facility is permissible in the relevant park zone.

Whether directional drilling can reduce surface disturbance.

Whether the project affects scenery, habitats, groundwater, or protected ecosystems.

Whether the location and design satisfy applicable park-protection requirements.

Legal principle: a developer's ownership or lease of surface land does not eliminate restrictions imposed by national-park legislation.

2.3 Environmental Impact Assessment Act, 1997

The Environmental Impact Assessment Act establishes procedures for assessing environmental impacts before certain projects proceed.

Geothermal projects must be examined against the Act's project categories, scale thresholds, and applicable procedures. The legal position should be checked for the particular project; not every geothermal installation automatically follows an identical assessment process.

The assessment process can address matters such as:

Noise and vibration from drilling and construction.

Impacts on flora, fauna, and protected landscapes.

Water quality and the management of geothermal fluids.

Air emissions and non-condensable gases.

Cumulative effects on hot springs and neighbouring developments.

Monitoring, mitigation, and post-construction management.

The Ministry of the Environment publishes the Act and its implementing framework.

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Advanced technologies do not necessarily eliminate assessment obligations. A smaller surface footprint may reduce some impacts, but deep drilling, fluid injection, and reservoir stimulation may introduce risks that require additional technical investigation.

2.4 Electricity Business Act, 1964

The Electricity Business Act provides the wider legal framework for electricity businesses and generating facilities.

A geothermal operator must determine which business-related notifications, registrations, technical standards, inspections, and other requirements apply to its specific generating arrangement.

For example, a binary-cycle plant uses heat from geothermal fluids to vaporise a secondary working fluid. This may change the plant's engineering and operational risk profile, but it does not remove applicable electrical safety requirements.

The relevant compliance questions include:

Whether the plant's generation and supply activities trigger business-related requirements.

Whether generating equipment and associated electrical installations meet applicable technical standards.

Whether construction, maintenance, inspections, and accident reporting obligations apply.

Whether changes to the generating system require additional filings or safety assessments.

2.5 Other relevant legislation

Forest Act: Projects involving forest development, access roads, or protected forest land may require additional authorisation.

Water Pollution Prevention Act: Discharges and other regulated activities must be assessed against the applicable water-quality requirements. Reinjection into a geothermal reservoir and discharge into surface waters are legally different operations.

Basic Act on Energy Policy: This Act supplies general policy principles rather than a stand-alone drilling permit. Energy security, environmental compatibility, and efficient energy supply inform the wider policy setting.

Renewable-energy support framework: Eligible geothermal projects may qualify for support under the applicable renewable-energy scheme. Financial eligibility does not substitute for environmental, land-use, or safety permissions.

3. Regulatory institutions and their functions

Ministry of the Environment (MOE)

Develops environmental policy and guidance on hot-spring protection, natural parks, and environmental assessment.

Ministry of Economy, Trade and Industry (METI)

Oversees energy policy, electricity-sector regulation, industrial safety, and relevant geothermal project assessment procedures.

Prefectural governors and local authorities

Administer relevant drilling permits, hot-spring protections, local land-use controls, and other delegated or locally applicable requirements.

Japan Organization for Metals and Energy Security (JOGMEC)

Supports geothermal resource development through relevant surveys, technical assistance, and eligible financial or risk-sharing mechanisms.

The division of responsibilities matters because a geothermal developer may need to coordinate several procedures with different authorities. The Ministry of the Environment's hot-spring guidelines are technical and administrative guidance, while statutory permissions derive from the relevant legislation.

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4. Regulation of specific advanced geothermal technologies

4.1 Enhanced Geothermal Systems (EGS)

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EGS aims to extract heat from hot underground rock where natural fluid flow or permeability is insufficient. The operator may inject fluid and use controlled stimulation to improve underground flow pathways.

The legal concerns are more complex than ordinary drilling because the project may affect underground pressure, nearby hot springs, groundwater, and seismic activity.

Principal legal questions

Does the proposed drilling require permission under the Hot Springs Act?

Does injection or stimulation affect a protected water resource or trigger other environmental requirements?

Could the operation cause induced seismicity or damage to neighbouring property?

Does the site lie within a national park or protected forest?

What monitoring, emergency response, and remediation measures are legally required or appropriate?

A well designed for EGS may require extensive geological surveys and a baseline record of local seismicity, groundwater quality, hot-spring temperature, and flow rates.

Legal analysis: Japan's conventional hot-spring legislation does not, by itself, provide a complete and dedicated statutory code for every EGS technique. The developer must therefore assess each operation under the existing laws applicable to its purpose, location, and physical effects.

4.2 Deep and directional drilling

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Directional drilling allows operators to reach a subsurface target from a surface location that may be some distance away. This can reduce the number of surface pads and help avoid sensitive areas.

However, it can also create uncertainty about the interaction between neighbouring underground resources.

For example, a directional well might pass beneath a hot-spring resort while its surface drilling pad is outside the resort. Whether a permit is needed depends on the applicable statutory provisions and the actual drilling purpose; the surface location alone does not resolve the question.

The Environment Ministry's geothermal guidance addresses the protection of hot-spring resources and the scientific basis for decisions concerning geothermal drilling. It has also published monitoring guidance, including material on IoT-based monitoring.

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Recommended regulatory safeguards include:

Geological and hydrogeological baseline studies.

Well-casing and cement-integrity testing.

Monitoring of nearby springs and groundwater.

Recording of drilling-fluid losses and abnormal pressure changes.

Contingency plans for well failure and unexpected gas release.

Proper well closure and site restoration.

These measures may arise from specific permit conditions, technical requirements, environmental assessments, or recognised good practice; they should not all be described as universal standalone statutory duties.

4.3 Closed-loop geothermal systems

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Closed-loop systems transfer heat through sealed pipes rather than deliberately extracting geothermal water through a production well. They may therefore reduce the risk of disturbing the chemistry or flow of existing hot springs.

Their legal treatment still depends on the engineering design. Relevant questions include:

Whether drilling falls within the Hot Springs Act's definition and purpose requirements.

Whether drilling, excavation, or infrastructure is restricted at the site.

Whether the system's fluid or materials present contamination risks.

Whether the installation is subject to electricity-safety requirements.

Whether the project falls within an applicable environmental assessment category.

Important distinction: a closed-loop design can reduce certain environmental risks, but it is not automatically exempt from Japanese environmental and land-use legislation.

4.4 Supercritical geothermal systems

Supercritical geothermal projects seek to exploit very high-temperature resources at depth, potentially offering substantial energy output from relatively compact surface facilities.

They also present difficult engineering and regulatory challenges:

Extreme temperatures and pressures.

Corrosion and mineral deposition.

Uncertain reservoir behaviour.

High-temperature well-integrity risks.

Limited operational experience in some geological conditions.

The legal challenge is how to evaluate safety when established regulatory practices may not fully reflect the technology's operating conditions.

A sound permitting approach should use current scientific evidence, independent technical review where appropriate, documented safety assumptions, and monitoring capable of detecting deviations from predicted behaviour.

4.5 Binary-cycle plants and advanced geothermal monitoring

Binary-cycle systems can generate electricity from geothermal heat through a secondary working fluid. Advanced monitoring systems can track reservoir pressure, temperature, chemistry, well performance, and seismic activity.

Monitoring data may become legally important evidence in disputes about whether an operator has damaged neighbouring resources or complied with permit conditions.

For example, if a nearby hot spring's flow decreases after geothermal production begins, time-series measurements may help establish whether the decline is connected to the project or to other geological or climatic causes.

Japan's Environment Ministry publishes geothermal-specific hot-spring protection guidance and an IoT monitoring manual, supporting a more evidence-based approach to resource management.

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5. Case law and judicial principles

A crucial qualification is necessary: I could not verify a reported Japanese Supreme Court judgment specifically establishing the legality of EGS stimulation, supercritical geothermal drilling, or a closed-loop geothermal power project. The cases below are therefore relevant judicial authorities and analogous disputes, not direct precedents deciding those technologies.

This distinction matters in academic legal writing. A geothermal policy document, an administrative dispute, a patent judgment, and a binding judicial precedent are not interchangeable.

Case 1: Ikata Nuclear Power Plant case

Supreme Court of Japan, 29 October 1992 · Case No. 1985 (Gyo-Tsu) 133

Official judgment: Supreme Court judgment and summary

Facts and issue: Residents challenged the administrative permission granted for the installation of nuclear reactors. The dispute concerned the adequacy of the technical safety assessment conducted by the authorities.

Decision: The Supreme Court dismissed the appeal. It explained that judicial review should examine whether the scientific and technical assessment contains unreasonable criteria or serious errors and omissions. The Court also discussed the evidential responsibilities of the parties.

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Relevance to geothermal law

The judgment is not a geothermal case, but its approach provides a useful framework for challenges to technically complex energy decisions.

Suppose an authority approves an EGS project despite evidence that its induced-seismicity model omits a significant fault system. A court applying analogous principles might examine whether the technical criteria and assessment process were reasonable in light of the scientific evidence.

The judgment does not mean that courts must defer to every expert opinion. It recognises that serious deficiencies in the technical assessment may undermine the legality of an administrative decision.

Legal principle: technical complexity does not remove an energy project from judicial review.

Case 2: Minamata disease state-liability judgment

Supreme Court of Japan, 15 October 2004 · Case No. 2001 (O) 1194

Official judgment: Supreme Court judgment and summary

Facts and issue: The litigation concerned serious health damage from mercury pollution and whether the national government had unlawfully failed to exercise regulatory powers to prevent further harm.

Decision: The Supreme Court held that the government's failure to exercise relevant regulatory powers was unlawful in the circumstances established by the case. The Court considered the government's knowledge of the danger and its ability to take preventive action.

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Relevance to geothermal law

The judgment is relevant by analogy to regulatory oversight of environmental risks.

Suppose an operator's geothermal activities cause groundwater contamination and the responsible authorities possess credible evidence of continuing harm. The case illustrates why regulatory powers cannot necessarily be left unused when the legal conditions for intervention are satisfied.

However, the Minamata judgment does not establish a geothermal-specific duty to stop a project whenever environmental harm is alleged. The applicable statute, evidence, available powers, and circumstances would determine the result.

Legal principle: regulatory inaction may give rise to state liability where the legal conditions for intervention and the requirements of unlawfulness are satisfied.

Case 3: Hot-spring rights and drilling disputes

Japan has a body of hot-spring-related legal disputes involving the legal character of hot-spring rights, drilling, and restrictions affecting existing sources. The Japan Spa Association's published case-law index identifies discussions of disputes concerning newly drilled springs and the legality of restrictions in specially protected hot-spring areas.

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These materials are relevant to geothermal projects, but an index of case studies is not enough to establish the precise facts, holdings, or precedential status of any particular decision. A formal case citation and the full judgment should be obtained before relying on a specific hot-spring dispute as authority.

Legal issues raised by this line of disputes include:

Whether an operator has a legally protected interest in an existing hot spring.

Whether drilling restrictions are authorised by the applicable law.

Whether a restriction is supported by scientific evidence.

Whether the legal interests of existing users outweigh or constrain a proposed development.

Whether the operator can seek administrative review or civil relief.

For an EGS project, evidence of a connection between the new well and an existing hot spring may become critical. A decline in spring flow alone does not automatically prove causation or establish the legal remedy.

Case 4: Geothermal development disputes under Japan's FIT scheme

Naoki Masuhara, Geothermal Power Developments and Related Disputes under FIT Scheme in Japan, 2021

Research article: Read the study on J-STAGE

This is an academic study, not a court judgment. It examined geothermal development disputes in Japan between 2011 and 2020 and considered the relationship between local disputes and geothermal development conditions. It identifies local understanding and acceptance as important issues in expanding geothermal power.

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Its relevance is practical as well as legal. A project may be technically feasible and potentially eligible for renewable-energy support while still encountering opposition over hot-spring resources, environmental impacts, and local economic interests.

Legal lesson: financial support and technical feasibility cannot substitute for compliance with permitting requirements or effective management of local environmental concerns.

6. Legal liability, enforcement, and remedies

Advanced geothermal projects may generate several kinds of legal disputes. The appropriate remedy depends on the statutory violation, the harm suffered, and the legal relationship between the parties.

6.1 Civil liability

Where geothermal operations cause injury or property damage, possible claims may arise under the Japanese Civil Code, including its tort provisions.

The claimant may need to establish legally relevant elements such as wrongful conduct, damage, causation, and fault where required by the applicable cause of action.

For example, if drilling-related activity causes subsidence or damages a neighbouring facility, the evidence might include seismic records, well-pressure data, geological modelling, and expert reports.

The existence of a geothermal permit does not automatically eliminate civil liability for independently unlawful conduct or damage.

6.2 Administrative litigation

The Administrative Case Litigation Act provides routes for challenging certain administrative dispositions. Whether a local resident, hot-spring operator, or environmental organisation may bring a particular action depends on the applicable statutory requirements, including the nature of the decision and the claimant's legally protected interest.

Potential issues include:

Whether the authority applied the correct legal standard.

Whether relevant scientific evidence was adequately examined.

Whether the authority overlooked a material risk.

Whether the decision exceeded or abused its discretionary powers.

Whether procedural requirements were satisfied.

The Ikata judgment is relevant to the judicial examination of expert technical assessments, but its nuclear licensing context must be kept in mind.

6.3 State liability

Article 1(1) of Japan's State Redress Act provides a framework for compensation where a public officer unlawfully causes damage through the exercise of public authority, subject to the statutory requirements.

The Minamata judgment demonstrates that failure to exercise regulatory powers can, in appropriate circumstances, be unlawful. It does not mean that every failure to regulate a geothermal project gives rise to compensation.

7. Regulatory challenges specific to advanced geothermal energy

A. Protection of hot springs

Geothermal extraction can alter pressure, temperature, or water flow in interconnected underground systems. Baseline monitoring and continued comparison with neighbouring springs are important safeguards.

B. Induced seismicity

Injection and reservoir stimulation can change underground stress. Risk management should address baseline seismicity, operational thresholds, monitoring, and contingency responses appropriate to the site.

C. Regulatory uncertainty

Japan's geothermal regime is distributed across multiple statutes. Developers must identify the applicable permissions individually rather than assume one general geothermal licence covers the entire project.

D. Community acceptance

Hot-spring operators may depend on the stability and quality of local water resources. Transparent monitoring, communication of risks, and credible responses to complaints can reduce disputes.

E. Emerging technologies

Closed-loop systems, EGS, and supercritical geothermal methods may present risks not fully addressed by older technical assumptions. Regulatory guidance should adapt to reliable scientific evidence while remaining consistent with statutory authority.

The continuing need to reconcile geothermal development with local concerns is also reflected in the academic literature on Japanese geothermal disputes.

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8. Hypothetical case study: EGS project near a hot-spring resort

Assume a company proposes an EGS power plant near an established hot-spring resort in a volcanic region of Japan.

The company intends to drill deep wells, inject water to improve underground permeability, and extract heat for electricity generation.

Legal assessment of the project

Drilling permission: Determine whether the proposed wells fall within the Hot Springs Act's drilling requirements and obtain any required permissions.

Protected-area compliance: Establish whether the drilling pads, roads, pipelines, and generating plant are subject to Natural Parks Act restrictions.

Environmental assessment: Determine which environmental assessment procedures apply and evaluate groundwater, noise, ecology, and other relevant effects.

Reservoir-risk assessment: Model underground pressure, fault structures, potential seismicity, and hydraulic connections with existing hot springs.

Operational safeguards: Establish monitoring procedures, appropriate response thresholds, emergency arrangements, and well-integrity controls.

Dispute prevention: Engage the local community and hot-spring operators, disclose relevant monitoring results, and establish procedures for investigating complaints.

Possible legal outcomes

Scenario A — No demonstrated adverse effect: If the project meets all applicable legal requirements and its technical assessment is adequate, it may proceed subject to relevant permissions and conditions.

Scenario B — Evidence of a serious deficiency: If the assessment fails to account for a significant geological fault or a plausible connection to a protected hot spring, the authority may need to reconsider the matter within its statutory powers. A court could review the legality of the resulting administrative decision.

Scenario C — Damage during operation: If credible evidence establishes that geothermal operations caused legally actionable damage, the operator may face regulatory measures and civil claims. Compensation and other remedies depend on the facts and the applicable legal rules.

These are hypothetical applications of Japanese law, not outcomes of an actual EGS court judgment.

9. Recommended legal and regulatory reforms

Japan could strengthen its geothermal framework through the following measures.

1. Clarify geothermal resource rights. Establish clearer rules concerning competing subsurface uses, resource interference, and the relationship between surface ownership and geothermal development.

2. Develop technology-specific standards. Provide detailed guidance for EGS stimulation, deep directional drilling, closed-loop systems, and supercritical resources.

3. Improve cumulative-impact assessment. Assess multiple wells and neighbouring projects together where their combined effects may affect a shared reservoir or hot-spring system.

4. Strengthen monitoring and disclosure. Establish appropriate requirements for baseline data, ongoing measurements, incident reporting, and access to relevant environmental information.

5. Improve coordination between authorities. Reduce inconsistencies between environmental, hot-spring, park, land-use, and electricity-related procedures.

6. Clarify dispute-resolution arrangements. Improve access to technical evidence, independent assessment, and proportionate remedies for affected communities.

7. Use adaptive regulation. Permit conditions and technical guidance should respond to new evidence without undermining legal certainty or bypassing statutory procedures.

These proposals would build on the existing framework rather than imply that Japan presently has a single, comprehensive geothermal statute.

10. Conclusion

Japan regulates advanced geothermal technologies through a combination of the Hot Springs Act, Natural Parks Act, Environmental Impact Assessment Act, Electricity Business Act, and other applicable laws.

The key legal difficulty is that the country's geothermal resources often overlap with valuable hot springs and protected natural environments, while advanced technologies introduce technical risks that may differ from those of conventional geothermal production.

The principal judicial authorities discussed above provide useful guidance on technical administrative review and environmental regulatory responsibility, but they must be distinguished from direct geothermal precedents. The Ikata nuclear judgment concerns judicial scrutiny of expert safety assessments; the Minamata judgment concerns unlawful regulatory inaction in an environmental-health disaster. Neither directly determines the legality of EGS or supercritical geothermal development.

The strongest legal approach is therefore to combine careful statutory interpretation, reliable geological evidence, transparent monitoring, compliance with project-specific permissions, and meaningful engagement with affected communities.

Primary sources and further reading

Ministry of the Environment, Japan — Hot Springs Act and geothermal protection guidelines.

Ministry of the Environment, Japan — Environmental Impact Assessment Act.

Supreme Court of Japan — Ikata Nuclear Power Plant judgment, 29 October 1992.

Supreme Court of Japan — Minamata disease state-liability judgment, 15 October 2004.

Naoki Masuhara — Geothermal Power Developments and Related Disputes under FIT Scheme in Japan.

Academic-use note: This is a general legal overview, not a substitute for checking the current Japanese statutory text, implementing regulations, prefectural rules, and project-specific permit conditions. Japanese case-law holdings should be verified from the full judgments before being relied on in litigation or formal legal research.