• • Can an approved settlement agreement or its provisions on maintenance serve as a barrier to a subsequent court application with a lawsuit for alimony?

• • Is such a lawsuit considered an attempt by a party to review an already resolved identical dispute (re-litigation ), or does it act as a new way of protecting the child’s rights due to a change in circumstances?

• • How do the provisions of Article 181 of the Family Code of Ukraine (regarding methods of fulfilling the obligation by agreement) correlate with the right to judicial protection if the current terms of the agreement are insufficient to ensure the child’s interests?

• 1. Analysis of the substantive legal nature of alimony: the concept of alimony as the property of the child is studied, which limits the contractual freedom of parents and does not allow them to enter into agreements that effectively lead to a waiver of this right.

• 2. Assessment of the dynamic nature of family rights: the relationship between the principle of res judicata and the continuing nature of alimony obligations, which implies the possibility of their review, is examined.

• 3. Application of the rebus sic stantibus doctrine (change in circumstances): the impact of unpredictable factors (the beginning of a full-scale war, a decrease in income, the child reaching the age of 14 and their right to choose their place of residence) on the binding nature of the settlement agreement is analysed.

• 4. Functional analysis of the “best interests of the child” criterion: the principle is viewed as a universal filter through which all procedural decisions and substantive legal agreements of parents must pass.

• 5. Study of the procedural role of the court: the limits of the active role of the court (ex officio) in child maintenance cases are determined, where the court is obliged to go beyond passive consideration for the collection of evidence and assessment of the real financial circumstances of the parties.

When making any decision, subjects of legal relations, in the person of both state bodies and courts, are obliged to adhere to the rule of law. This principle is accepted as a collective concept that includes components such as legality, prevention of abuse of power, checks and balances, equality and non-discrimination, access to justice, constitutional review and legal certainty, according to the report approved by the Venice Commission in 2011.¹ At the same time, one of the elements of legal certainty is precisely the adherence to the principle of res judicata, which is not just a theoretical position but the foundation of any stable legal system, an axiom that a final judicial decision cannot be questioned, and a rule constantly applied by courts.

Accordingly, the principle of res judicata has been repeatedly declared at the international level, particularly in paragraph 148 of the ELI-UNIDROIT Model Rules of European Civil Procedure² or paragraph 1 of Article 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms.³ Furthermore, the European Court of Human Rights has directly interpreted this principle in its decisions such as Brumarescu v. Romania, ⁴ Sunday Times v. United Kingdom, ⁵ Naumenko v. Ukraine, ⁶ or Ryabykh v. Russia.⁷ According to it, no party has the right to demand a review of a final and binding court decision solely for the purpose of achieving a re-hearing and the issuance of a new decision in the case. The review powers of higher courts should be exercised to correct judicial errors and deficiencies, rather than for a new trial. Violation of this principle is a breach of the guarantees for ensuring a fair trial, particularly for those who rely on the validity of the decision.

However, a departure from res judicata is possible and necessary when required by relevant compelling and insurmountable circumstances. A court-approved settlement agreement cannot be viewed as an insurmountable procedural barrier that forever deprives a child of the right to receive proper maintenance from a parent. If the terms of such an agreement have ceased to correspond to the best interests of the child due to a substantial change in circumstances, the court has not only the right but also the duty to intervene to restore the balance of rights.

Modern European doctrine of civil procedure and family law proceeds from the fact that the binding and final nature of a judicial decision in cases regarding continuing obligations (in particular, child maintenance) is not absolute and is subject to a change in factual circumstances. Agreements regarding the material maintenance of a child are based on the current state of affairs, i.e., the rebus sic stantibus doctrine. A substantial change in circumstances creates a fundamentally new legal situation that objectively could not have been the subject of consideration during the approval of the original settlement agreement.

For example, the ELI-UNIDROIT Model Rules of European Civil Procedure, although oriented towards the stability of decisions, in Rule 182 (“Extraordinary Recourse”), provide for the possibility of reviewing final decisions if they are based on facts that subsequently substantially changed their character.

In view of this, the procedural form of a settlement agreement cannot limit access to justice if its material basis has ceased to exist or has fundamentally changed. A refusal to protect a child’s rights solely due to the existence of an agreement concluded under different factual circumstances is a manifestation of excessive formalism, which violates Article 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms.

Therefore, filing a new lawsuit for alimony recovery in the presence of a valid settlement agreement is not an attempt by a party to review an already resolved identical dispute (abuse in the form of re-litigation ). Such a lawsuit constitutes a new and independent way of protecting the child’s rights, as it is based on the appearance of new factual circumstances to which the principle of res judicata of the previously issued court ruling does not apply.

Unlike classic civil relations, where the autonomy of the will of the parties prevails, the sphere of childhood is under the special care of the state. A child is not simply an “object” of parental care; they are an autonomous subject of law whose needs have public significance.

The fundamental basis for understanding the limits of parental contractual freedom is the substantive legal nature of alimony. In particular, for example, according to the first part of Article 179 of the Family Code of Ukraine, alimony received for a child is the property of the child themselves.⁸ The parent in whose name it is paid is not its owner but acts only as a manager who is obliged to use the funds exclusively for their intended purpose in the child’s interests. Since the right of ownership of alimony belongs to the child, parents do not have the authority to enter into agreements that effectively lead to a waiver of this right or its significant limitation. Any settlement agreement that violates the child’s right to proper maintenance contradicts the very essence of the legislation.

The universal nature of the principle of the best interests of the child, which is enshrined in Article 3 of the Convention on the Rights of the Child, requires from the court not a formal but a substantive approach.⁹ This criterion acts as a “universal filter” through which all procedural decisions and substantive legal agreements of parents must pass.

Analysing General Comment No. 14 (2013) on the right of the child to have their best interests given primary consideration, the best interests of the child has a triune nature: it is simultaneously the child’s right to primary consideration of their interests, a fundamental legal principle of interpretation of norms, and a procedural rule requiring an assessment of the impact of any decision on the child. In the assessment, it is necessary to consider elements such as: the child’s views, their individuality, the necessity of preserving the family environment, care, protection and safety, vulnerable status, the right to health, and the right to education.¹⁰

Due to its flexibility, the concept of the best interests of the child allows for adaptation to a specific situation and changes according to the child’s development and external circumstances. It is worth noting that the older the child, the more their position should be considered. According to the principles of the Commission on European Family Law (CEFL) regarding parental responsibility and regarding maintenance, the child’s autonomy should be respected in accordance with the developing ability and need of the child to act independently.¹¹ In particular, the child reaching the age of 14 gives them the right to independently determine their place of residence, which is a key element in assessing their interests and can completely nullify the parents’ previous agreements on the order of residence and maintenance.

The principle of the best interests of the child is also enshrined in Article 24 of the Charter of Fundamental Rights of the European Union.¹² It is widely applied by the European Court of Human Rights, particularly in cases such as C v. Croatia regarding a violation in the court’s failure to hear the child’s opinion,¹³ or M. K. v. Greece regarding taking the opinion of a 13-year-old child into account.¹⁴

Additionally, the concept of the best interests of the child is one of the central concepts to the Council of Europe Committee of Ministers’ Guidelines on Child-friendly justice.¹⁵ According to these guidelines, justice is “child-friendly” only when it is adapted to the child’s needs and ensures the effective exercise of their rights, taking due account of their maturity and level of understanding. In the context of alimony disputes, this standard implies that the court must not be a passive observer but must actively ensure that the legal process serves the current well-being of the minor.

The Ukrainian Supreme Court also does not lag behind international practice: there is a broad international and national consensus that in all decisions, ensuring the best interests of the child must be of primary importance. Depending on the nature and seriousness, these interests may exceed the interests of parents, including their desire to adhere to the terms of previously concluded agreements.¹⁶

In the context of alimony disputes, this means that any private parental agreements should be considered relevant only as long as they serve the child’s good. If a settlement agreement ceases to correspond to their best interests and becomes a tool for limiting their rights, the “filter” of Article 3 of the Convention requires the court to prioritise the protection of the minor’s rights over the principle of the stability of private agreements, and the terms of the agreement must be immediately changed or supplemented.

The tendency towards limiting the absolute effect of the res judicata principle and freedom of contract in family legal relations in favour of the concept of the best interests of the child is characteristic of most leading legal systems of the European Union. A comparative analysis of the family legislation of EU countries demonstrates that settlement agreements between parents are recognised as an important tool; however, they are always under strict judicial control and are subject to unconditional review in case of a change in circumstances.

According to the Civil Code of France (Code civil ), parents can independently settle the issue of child maintenance by concluding an agreement (Art. 373–2-2). However, the French legislator limits the effect of the principle of the immutability of such contracts. According to Articles 373–2-13 and 373–2-6 of the Code civil, the family court judge (Juge aux affaires familiales) is empowered at any time to change or supplement the parents’ agreement if the child’s interests require it or if new factual circumstances (des faits nouveaux) have arisen.¹⁷ That is, French doctrine directly recognises that the child’s interests always prevail over the finality of previous agreements.

The legal system of Poland, which is conceptually close to the Ukrainian one, also contains direct indications of the possibility of overcoming res judicata in alimony disputes. According to Article 138 of the Family and Guardianship Code of Poland (Kodeks rodzinny i opiekuńczy), in case of a change in circumstances, each party may demand a change in the court decision or agreement regarding the alimony obligation (W razie zmiany stosunków można żądać zmiany orzeczenia lub umowy dotyczącej obowiązku alimentacyjnego).¹⁸

Thus, the European legal tradition is unanimous in its approach: alimony obligations have a continuing and changeable character. Any private agreements or court orders by which they are approved have legal force only as long as they effectively ensure the best interests of the child in current realities. A refusal to review such agreements through a formal reference to the stability of a judicial decision contradicts not only Ukrainian legislation but also the fundamental principles of European procedural law.

The problem of competition between procedural dogmas and the real needs of the child is most clearly revealed in a civil case, the dispute in which is a classic example of a legal conflict between the peaceful contractual regulation of child maintenance and the necessity for flexible judicial protection in conditions of an extraordinary change in circumstances caused by war.¹⁹

In April 2021, in a relatively stable pre-war period, the Desnianskyi District Court of Kyiv approved a settlement agreement between the parents.²⁰ The parties agreed on a parity model: each parent maintains the son independently and at their own expense exclusively during his residence with them. This agreement, calculated until the child’s majority, subsequently became that formal shield (res judicata) behind which the defendant (mother) and the lower courts hid their unwillingness to react to new life realities.

The key error of law enforcement in the analysed case was the courts’ ignorance of the fundamental change in factual circumstances (rebus sic stantibus doctrine). At the moment of concluding the settlement agreement in 2021, the parties could not objectively have foreseen the full-scale invasion of the Russian Federation, which completely destroyed the economic and security situation in the country.

The change in circumstances due to martial law required from the courts an assessment of the situation from several aspects at once, as the war directly affected the child’s life support – firstly, the vulnerability and security needs in war conditions. The change in the security and economic situation in Ukraine after February 2022 places the child in a vulnerable position. The very fact of the child’s presence in a country where war is ongoing objectively requires significantly greater financial support than was envisioned by the parties in 2021.

Secondly, the economic imbalance, as the full-scale invasion led to a significant decrease in the income of the plaintiff (father), who remained with the child in Ukraine. At the same time, the defendant (mother), who is in safety in the Kingdom of Spain and has a stable income, completely withdrew from financing the son, referring to the outdated settlement agreement.

Thirdly, the change in life priorities and the child’s autonomy, as they reached the age of 14 and, having the legal right to independently determine their place of residence, consciously chose to stay with the father. Moreover, in war conditions, the son studies at a boarding school, which creates specific educational and household expenses that could not have been forseen.

Despite these glaring changes, the courts of the first and appellate instances denied the lawsuit, supporting the mother’s position. They effectively preserved the pre-war agreements, applying the ruling approving the settlement agreement as an absolute procedural barrier. The courts ignored the aspect of the continuing indirect impact of the long-term martial law on the child’s provision.

Such an approach by the courts is not only a manifestation of excessive formalism but also a dangerous precedent. A refusal to protect a child’s rights solely due to the existence of an agreement concluded under entirely different factual circumstances creates artificial barriers to access to justice and contradicts Article 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms. A settlement agreement remains mandatory only as long as new unpredictable factors – even more so war – do not turn it from a protection tool into a means of limiting the child’s rights.

Reviewing the decisions of the lower courts in the investigated case, the Civil Cassation Court within the Supreme Court overturned them, pointing out gross errors in the application of the law. The Supreme Court formulated fundamental conclusions regarding the limits of dispositivity, the effect of the settlement agreement, and the court’s duties in family disputes.

Primarily, the Supreme Court drew attention to the legal nature of a settlement agreement. Relying on the practice of the Grand Chamber, the Court stated that a settlement agreement is a contract entered into by the parties for the purpose of terminating the dispute and an act that concludes the proceedings. However, the closure of proceedings in a case does not mean the automatic loss of the right to judicial protection in the future.

This conclusion acquired special significance in the context of alimony legal relations, which have a continuing and imperative character. The Supreme Court explained that the existence of a court-approved settlement agreement does not exclude the possibility of a new judicial trial in case of a change in the grounds or subject of the lawsuit. The basis for satisfying such an application is establishing the fact of a change in circumstances or a conclusion that the current arrangement does not provide the child with proper and stable maintenance.

Thus, filing a new lawsuit for alimony recovery is not an attempt to review an identical dispute. It is a new and independent way of protecting the child’s rights, as it is based on a change in factual circumstances to which the principle of res judicata of the previous court ruling does not apply.

The Court also pointed out that the lawsuit is essentially being filed for the first time: although in 2021 the parties agreed on the maintenance issue (each maintains during residence with them), the size of the alimony itself in a fixed sum or a share of income was not agreed upon in it.

In its resolution, the Supreme Court emphasised that the relations between parents and children do not have an absolutely dispositive character and are under the enhanced protection of the state, and alimony received for a child is their property and must be used for its intended purpose.

The Court emphasised that the child is not a party to the parents’ settlement agreement. Their right to proper maintenance is autonomous and cannot be finally limited by private agreements of legal representatives if these agreements have ceased to correspond to the “best interests” criterion (Article 3 of the UN Convention on the Rights of the Child). Legal representatives do not have the authority to enter into agreements that in the future deprive the child of the right to proper maintenance. Accordingly, no provision of a settlement agreement can block the right to access to justice.

The Court pointed out that since the child currently resides with the father, who cares for them and provides everything necessary, this fact “contrary to the requirements of the law remained outside the attention of the appellate court,” as the mother’s lack of financial participation contradicts the intended purpose of alimony.

The passivity of the lower instances was subjected to the sharpest criticism by the Supreme Court. The appellate court, giving priority to the res judicata principle, effectively ignored the dynamic nature of family circumstances. The Supreme Court directly qualified such a refusal to protect the child’s rights solely due to the existence of an agreement concluded under other factual circumstances as a manifestation of “excessive judicial formalism,” which creates artificial barriers to access to justice and contradicts Article 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms.

The Supreme Court formulated a clear imperative for courts: “During the consideration of this case, based on the balance of interests of parents and the child, the court’s procedural duty includes finding out to what extent the substantial conditions that were the basis for concluding the settlement agreement have changed.” The appellate instance was obliged to assess the force majeure circumstances, the plaintiff’s assertions regarding a significant decrease in the level of income after February 2022, and the presence of another young child under maintenance.

The son reaching the age of 14 grants him, by law, the right to independently determine his place of residence. The Court emphasised that this fact nullifies the basic condition of the settlement agreement regarding “alternate residence” and “independent maintenance by the parent with whom the child resides,” as the child consciously chose to live with the father. Furthermore, the son’s studies at a boarding school create expenses that may not be covered by the previous agreement.

Thus, the Supreme Court overturned the decisions of the lower instances precisely because they “did not establish the factual circumstances on which the correct resolution of the case depends, did not properly check the parties’ arguments and the evidence provided for their confirmation,” restoring the priority of the child’s interests over the formalism of judicial procedures.