The Implications of Indonesian Inheritance Law Pluralism on the Rights and Portions of Inheritances for Adopted Children: A Comparative Doctrinal Study and Exploration of Supreme Court Jurisprudence

Dr KRA Michael Josef Widijatmoko SH SpN

Universitas Djuanda Bogor

Lisza Nurchayatie SH MKn

Universitas Pembangunan Nasional “Veteran” Jakarta

I. Juridical Introduction and Conceptual Framework

A. Background and Urgency of the Issue

Indonesia employs a pluralistic inheritance law system, where the applicable law depends on the religion and/or ethnic origin of the deceased, covering Islamic Inheritance Law (KHI) for Muslim residents, Civil Inheritance Law (Civil Code or KUHPerdata/BW) for non-Muslim residents, and local Customary Law (Hukum Adat). This pluralism, while reflecting societal diversity, creates significant complexity in determining civil status, particularly for adopted children (adopsi). The urgency of this study lies in the fundamental differences among these three systems regarding the recognition of blood ties (nasab) and civil relationships, which in turn generate legal uncertainty regarding the rights and portions of inheritance that adopted children can claim, both from their biological parents (OTK) and their adoptive parents (OTA).

The adoption of children is often driven by noble socio-economic reasons, such as the absence of offspring, compassion for orphans, or the biological parents’ inability to provide for the child. However, this social goodwill must be translated into formal legal procedures to protect the adopted child’s inheritance rights. Failure to formalize adoption through a court decree has proven to be a legal loophole detrimental to adopted children, causing inheritance conflicts and highlighting the gap between social practice and positive legal norms. Therefore, a deep, comparative doctrinal analysis and an exploration of Supreme Court (MA) jurisprudence are necessary to map the legal certainty offered by each system.

B. Legal Definition of Adopted Child and Formal Requirements for Adoption

The formal definition of an adopted child is crucial as it acts as the primary filter determining access to inheritance rights. According to Article 171 letter (h) of the Compilation of Islamic Law (KHI), an adopted child is defined as a child whose responsibility for daily upkeep, education costs, and so forth, is transferred from the original parents to the adoptive parents based on a Court Decision. This definition underscores that adoption is not merely a social act or an underhand agreement, but a legal action that must result in an official decree from the court, whether the District Court or the Religious Court, depending on the domicile and religion of the parties concerned.

This requirement for court formality is a non-negotiable legal prerequisite. The legality of adoption requires a product of a court decree, and not just a notarial deed or family agreement. Analysis shows that without this decree, the adopted child juridically lacks a strong legal basis to claim inheritance rights from their adoptive parents. The court decree serves as legitimacy, ensuring that the transfer of responsibility and the creation of the civil relationship have been implemented in accordance with prevailing laws and regulations. Consequently, the legality of adoption through a court decision is the critical determinant that opens the door for adopted children to claim Wasiat Wajibah (Mandatory Bequest) under KHI or a will/gift (hibah) under the BW.

C. Principles of Inheritance Law Related to Adoption

The position of the adopted child in inheritance is heavily influenced by the fundamental principles of the legal system used by the deceased:

1. Civil Law (KUHPerdata/BW)

The BW inheritance law adheres to the Parentela principle (system of heir categories) and the principle of testamentary freedom (testamentair erfrecht). Inheritance based on the law (ab intestato) is exclusively reserved for legal blood relatives or affinity, placing the adopted child de jure outside the line of statutory heirs. Although the deceased has the freedom to transfer assets through a will, this freedom is strictly limited by Legitieme Portie (LP) or the Reserved Portion of Legal Heirs. If an adopted child receives assets through a will that violates the LP of a biological child, the will can be contested and nullified, indicating a partial and fragile protection for the adopted child under the BW.

2. Islamic Law (KHI)

Islamic inheritance law adheres to the Ijbari principle (compulsory law, not testamentary freedom) and Bilateral (lineage based on blood ties/nasab). The nasab relationship is the main determinant of heir status (al-qarabah). Doctrinally, because adoption in Islam must not sever the child’s nasab from their biological parents , no nasab inheritance relationship arises between the adopted child and the adoptive parents. As a result, the adopted child cannot become a conventional heir of the adoptive parents, but the KHI provides a mechanism for civil protection through the doctrine of Wasiat Wajibah.

3. Customary Law (Hukum Adat)

Customary inheritance law is highly flexible and influenced by the local kinship system (patrilineal, matrilineal, or parental). The position of the adopted child is determined by the purpose of the adoption and local custom. If the adoption is intended to fully integrate the child into the family structure (e.g., to continue the lineage in a patrilineal system), the adopted child often acquires the same civil position and rights as a biological child, although there are exceptions for certain ancestral properties.

II. Legal Status of Adopted Child towards Biological Parents (OTK)

The inheritance status of an adopted child from their biological parents is a critical issue that distinguishes the impact of adoption under different legal systems, particularly between the KHI/Child Protection Law interpretation and the strict BW doctrine.

A. Preservation of Lineage (Nasab) in Islamic Law and the Child Protection Law

In the context of Islamic Law, child adoption is emphasized not to sever the blood relationship (nasab) between the adopted child and their biological parents. This key principle reflects the struggle of Muslims that was successfully accommodated in regulations and the Indonesian Ulema Council (MUI) Fatwa of 1984. The consequence of maintaining nasab is that the adopted child, although raised by adoptive parents, must still use their biological father’s name, as affirmed by Verse 5 of Surah Al-Ahzab.

The inheritance implication for Muslim Biological Parents (OTK) is that the adopted child retains the right to inherit assets from their OTK. The child is recognized as a legitimate heir based on the kinship relationship (al-qarabah) just like any other biological child, because their nasab relationship is not severed. The preservation of nasab provides dual protection: the child receives the guarantee of wasiat wajibah from the OTA (maximum 1/3) and retains full inheritance rights from their OTK.

B. Implications of Civil Relationship Severance (BW and Old Doctrine)

Historically and under pure Civil Law doctrine (BW) or old regulations governing adoption for specific groups (e.g., Stb. 1917 No. 129), child adoption was often regulated to sever all civil ties stemming from birth lineage. This means that after a legal adoption, the child is legally considered the legal child of the adoptive parents, but simultaneously, they lose civil rights and obligations from their biological family, including inheritance rights.

This old doctrine of total severance of civil ties creates a juridical contradiction, especially when faced with the principle of non-severance of nasab widely adopted by the KHI and mandated by the Child Protection Law (which favors the best interests of the child). If an adoption case—for example, in the Chinese community regulated under the BW—leads to the severance of nasab (a practice supported by some old court decisions), the adopted child will lose their inheritance rights from their OTK. This dual status indicates that the adopted child’s inheritance rights from the OTK heavily depend on the law chosen and applied during the adoption decree, although the modern legal trend in Indonesia moves towards child protection that prioritizes the continuity of nasab.

III. Analysis of Rights and Inheritance Portions of Adopted Children from Adoptive Parents (OTA)

The position of the adopted child’s inheritance rights towards Adoptive Parents (OTA) is the main point that causes the sharpest differences among the three legal systems in Indonesia.

A. Islamic Legal System (KHI): The Mechanism of Wasiat Wajibah

1. Basic Status and Protection Mechanism

Within the framework of Islamic Inheritance Law regulated in the KHI, an adopted child is fundamentally not an heir of the OTA due to the absence of a blood relationship (nasab). The adopted child is classified as dzawil arham or a distant relative who does not automatically receive inheritance. However, to provide substantive justice protection to the child who has been raised and educated, the KHI introduces the doctrine of Wasiat Wajibah (WW) (Mandatory Bequest). WW is a bequest required by law, the determination of which does not depend on the will of the deceased, but is established by the Religious Court as a legal obligation.

2. Maximum Portion and Distribution Procedure

Article 209 Paragraph (2) of the KHI stipulates that an adopted child who does not receive a bequest from the OTA is given a wasiat wajibah of a maximum of 1/3 (one-third) of the inheritance of their adoptive parents. The concept of the 1/3 portion is based on the hadith of Sa’ad bin Abi Waqash, which generally limits a bequest to a maximum of one-third of the total estate. The legal procedure affirms that the assets of this wasiat wajibah must be fulfilled first from the total estate of the deceased, before the remaining assets (2/3) are distributed to the legitimate nasab heirs.

3. Legal Obligation Related to Debt

It is important to note that because the adopted child does not have the status of a regular heir (nasab heir) under the KHI, they are legally not obligated to bear or pay the debts of their adoptive parents beyond the value of the assets they receive. The obligation of heirs to pay the debts of the deceased under Islamic law is limited only to the amount of the estate or inheritance. The status of the adopted child as a recipient of WW, not an heir, legally exempts them from fully bearing these debts.

B. Civil Legal System (KUHPerdata/BW): Bequest and the Limitation of Legitieme Portie

1. Basic Status and Mechanism of Inheritance Rights

In pure civil law (KUHPerdata), an adopted child is not recognized as an heir ab intestato (according to the law) . Therefore, the adopted child can only obtain the deceased’s assets from the OTA through a voluntary mechanism, namely a will (testamen) or a gift/grant (hibah) (donation during life) made legally. In the absence of a formalized will or grant, an adopted child subject to the BW has no legal basis to claim inheritance.

2. Restriction by Legitieme Portie

Although the OTA can make a will for the adopted child, the granting of assets must be subject to a strict limitation called Legitieme Portie (LP). The LP is the absolute right of legitimate heirs (biological children, parents, and spouses) to receive a minimum share of the inheritance. The granting of assets (both through will and grant) to an adopted child that exceeds the portion that can be freely willed (beschikbaar deel) and violates the LP of other legitimate heirs can be contested and legally nullified based on a court decision. This shows that the adopted child’s inheritance rights under the BW are very vulnerable and depend on careful estate planning by the OTA and the absence of a lawsuit from aggrieved legitieme heirs.

C. Customary Legal System (Hukum Adat): Principle of Status Equalization

Customary Law offers a highly contrasting perspective because the position of the adopted child is heavily influenced by local traditions and the purpose of the adoption.

1. Flexibility and the Principle of Equalization

In many customary communities, adoption is carried out with the goal of fully integrating the child into the family structure (inklaar), so that the adopted child acquires the same civil position as a biological child. An example is the Customary Community in Sesela Village, West Lombok, where the adopted child is called anak “akon” and has equal civil and inheritance rights with biological children, with the exception of certain ancestral properties (doe tengaq).

2. Influence of Syncretism

Although Customary Law tends to equalize status, in practice, the Customary inheritance system often undergoes syncretism with religious law. In Lombok, for example, the Customary distribution of inheritance is influenced by Islamic Law, resulting in a different division between males (“sepelembah”) and females (“sepersonan”). This complexity indicates that in Customary cases, judges must consider not only the pure local tradition but also the extent to which the tradition has been colored by other inheritance legal norms.

IV. Exploration of Supreme Court (MA) Jurisprudence and Legal Certainty

The role of Supreme Court (MA) jurisprudence is crucial in providing legal certainty and resolving disparities amid this pluralism, especially in the implementation of the Wasiat Wajibah doctrine in the Religious Courts.

A. Strengthening the Wasiat Wajibah Doctrine by Jurisprudence (KHI)

MA jurisprudence has become the main foundation for Religious Courts in guaranteeing the civil rights of Muslim adopted children. MA Decisions, such as Decision Number 04 K/AG/2011 and Decision Number 368 K/AG/1999 , explicitly affirm that adoptive parents and adopted children have a civil relationship in the form of wasiat wajibah.

Main Ratio Decidendi

The main Ratio Decidendi of these decisions is the stipulation that an adopted child who does not receive a will (or whose will is insufficient) is entitled to a wasiat wajibah of a maximum of 1/3 (one-third) of the adoptive parent’s estate, in accordance with Article 209 of the Compilation of Islamic Law . This jurisprudence provides an operational basis for Religious Court judges to grant financial legal protection to adopted children who are not entitled to inherit by nasab.

Furthermore, there is an expansion of the application of Wasiat Wajibah by jurisprudence. Although the KHI limits WW only to adopted children and adoptive parents , more progressive MA decisions sometimes extend this concept to non-Muslim relatives or stepchildren, giving them a share of the inheritance equivalent to Muslim heirs, but still limited to a maximum of 1/3 of the estate . This expansion reflects the judiciary’s effort to achieve substantive justice beyond the textual boundaries of the KHI.

B. Factors of Decision Disparity and Substantive Justice

Although the KHI and jurisprudence have set a maximum limit of 1/3, implementation in the field still shows disparity in determining the portion of wasiat wajibah given to adopted children . This disparity is not always a deviation but a reflection of the judge’s role as a law finder (rechtsvinder) who must balance various interests.

Balancing the Rights of Heirs

The main factor causing disparity is the consideration of fairness to nasab heirs (biological children). Religious Court judges sometimes do not automatically grant the full 1/3 portion to the adopted child but consider whether granting the maximum portion would violate the rights of legitimate biological heirs . The judge’s decision aims to ensure that the protection of the adopted child (who needs support) does not disproportionately sacrifice the primary inheritance rights of blood descendants.

Furthermore, the decision may differ if there is a valid will from the adoptive parents. If the OTA has left a valid will granting a certain share to the adopted child (even if below 1/3), the judge is obliged to follow the content of the will, provided it does not violate the rights of other heirs. This disparity indicates that 1/3 is the maximum limit of legal protection, not an absolute right automatically granted, and the final decision is always based on the Judicial Panel’s assessment of the conditions for justice in the case .

C. Legal Consequences of Invalid/Underhand Adoption

Legal analysis consistently shows that the formality of adoption through a court decree is the absolute key to claiming inheritance rights. An adopted child whose adoption was carried out informally or “underhand” does not have a strong legal basis to claim wasiat wajibah (KHI) or a will (BW).

Legal Risk Without Formality

Without a legal status, the adopted child is formally considered another person or a relative without an inheritance legal bond. If an inheritance dispute occurs, the adoptive family and legal heirs can argue that the adopted child is not entitled to the deceased’s assets, even though socially the child has been treated like a biological child. Empirical data shows that most adoptions in society occur without formal legal procedures, which inherently creates high vulnerability in inheritance claims and triggers family conflict .

Alternative Efforts

If the adoption is not legal, the only way for the adopted child to obtain assets is through legal actions taken by the OTA during their lifetime, such as an irrevocable grant (hibah) (if it does not violate the LP in the BW) or through an ordinary will. However, grants and wills depend on the deceased’s wishes, unlike wasiat wajibah, which is a compulsory legal guarantee that arises automatically if the adoption is formalized.

V. Conclusion and Juridical Recommendations

A. Comparative Synthesis and Implications for Adopted Children

The inheritance rights of adopted children in Indonesia are a clear reflection of the legal pluralism. The legal protection received by adopted children varies radically, depending on the legal system governing the deceased and, most importantly, the formality of the adoption decree.

This synthesis shows that the KHI provides the strongest minimum guarantee (maximum 1/3) through compulsory legal intervention (wasiat wajibah), provided the adoption is formalized. Conversely, the BW offers the most fragile protection, highly dependent on the active initiative of the OTA to make a will or grant, which remains at risk of being contested by legitieme heirs if it violates the LP. Customary Law, while offering the potential for full parity, is limited by local variation and the influence of local religious law.

B. Practical and Legislative Recommendations

Based on the doctrinal analysis and exploration of jurisprudence, there are several juridical recommendations to strengthen legal certainty and the protection of adopted children’s rights:

1. Absolute Emphasis on Adoption Formality: Relevant institutions and notaries must emphasize the importance of adoption decrees through court decisions. This formality is the only legal guarantee that opens the door for adopted children to claim inheritance rights legally, whether through wasiat wajibah in the Religious Court or the legitimization of adoption in the District Court. Underhand adoption is a legally dangerous practice.
2. Preventive Action for Adoptive Parents (OTA): Especially for OTAs subject to Civil Law (BW) who have biological children, the preventive measure of making a formal will or grant (hibah) before a Notary is a necessity. This document must be carefully drafted so that the transfer of assets to the adopted child does not exceed the freely disposable portion of the deceased and does not violate the Legitieme Portie of biological children.
3. Harmonization of Laws Regarding Civil Relationship Severance: Further legislative reform is needed to harmonize the principle of severance/non-severance of civil ties post-adoption. Given the modern legal trend (Child Protection Law) and KHI, which maintain nasab, the principle that adoption must sever the inheritance relationship with biological parents (old BW doctrine) needs to be reviewed to reduce the dualism of inheritance legal status and ensure maximum protection for the child.
4. Standardization of Wasiat Wajibah Application: Although the MA has set the 1/3 limit, clearer guidelines are needed for the Religious Courts to minimize decision disparity . These guidelines should include balanced criteria for assessing substantive justice, ensuring that the rights of adopted children are met without disproportionately sacrificing the rights of nasab heirs .

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