In Philippine law, a person’s name is not a mere matter of personal preference or parental whim; it is a matter of public interest. The Civil Code and the Family Code strictly regulate the use of surnames to ensure stability in identity and the orderly administration of justice. When one parent unilaterally changes a child’s surname without legal basis or the other parent's consent, it creates a legal conflict that requires specific judicial or administrative remedies.

The Legal Framework of Surnames

To understand the remedies, one must first identify the rules governing the initial choice of a surname:

Legitimate Children: Under Article 364 of the Civil Code, legitimate children shall principally use the surname of the father.
Illegitimate Children: Under Republic Act No. 9255 (amending Article 176 of the Family Code), illegitimate children shall use the surname of their mother. However, they may use the surname of their father if their filiation has been expressly recognized by the father through the record of birth appearing in the civil register, or when an admission in a public document or private handwritten instrument is made by the father.

A parent cannot simply decide to "drop" a father's surname or "adopt" a stepfather's surname for a child through informal means, such as enrollment in school or social media usage, if it contradicts the registered birth certificate.

Common Scenarios of Unauthorized Change

The "Stepfather" Scenario: A mother gets remarried and begins enrolling the child in school using the new husband’s surname to avoid confusion or social stigma.
The "Aversion" Scenario: A parent, following a bitter separation, unilaterally reverts the child's surname to their maiden name or a different name to "erase" the other parent's presence from the child’s life.
The Administrative Error: A parent provides false information to the Local Civil Registrar (LCR) to register a child under a specific surname despite the lack of legal recognition or marriage.

Judicial and Administrative Remedies

If a parent has illegally or unilaterally changed a child's surname, the aggrieved parent or the state can avail of the following remedies:

1. Petition for Change of Name (Rule 103, Rules of Court)

If a parent wishes to legally change a child’s name, they must file a petition in the Regional Trial Court (RTC) where the child resides. If a change was done unilaterally and informally, the other parent can challenge the validity of that change.

Grounds: The Supreme Court has ruled that a change of name is a privilege, not a right. Valid grounds include when the name is ridiculous, tainted with dishonor, or when the change is necessary to avoid confusion.
The "Grande v. Antonio" Doctrine: The Supreme Court clarified that even if an illegitimate child is recognized by the father, the use of the father's surname is permissive, not mandatory. However, once a name is registered, it cannot be changed without a court order involving all interested parties (including the other parent).

2. Cancellation or Correction of Entries (Rule 108, Rules of Court)

If a parent successfully registered an unauthorized surname in the Civil Registry through misrepresentation, the aggrieved parent may file a Petition for Cancellation or Correction of Entries under Rule 108.

Scope: This is used when the entry in the civil register is "substantial" (affecting status, filiation, or citizenship).
Requirement: The proceeding must be adversarial, meaning the parent who made the change, the Civil Registrar, and all interested parties must be notified and given a chance to oppose.

3. Injunction and Damages

When a parent uses an unauthorized surname in school records, passports, or social settings without changing the birth certificate, the aggrieved parent can file a civil case for Injunction under the Civil Code to restrain the other parent from using the unauthorized name.

Article 26 of the Civil Code: Protects against "vexing or humiliating" another on account of his religious beliefs, lowly station in life, or other personal differences. Unilaterally stripping a father's name from his child's public identity is often argued as a violation of the father's right to his name and his relationship with the child.

4. Mandatory Reversion through the Bureau of Immigration or DFA

If the unauthorized change has reached official documents like passports, the aggrieved parent can alert the Department of Foreign Affairs (DFA) or the Bureau of Immigration. These agencies generally require a birth certificate as the primary document. If the passport name deviates from the birth certificate without a court order, the document may be cancelled or its renewal denied until the discrepancy is corrected.

Crucial Jurisprudence

Republic vs. Capote: The Court held that a change of name is a proceeding in rem. Strict compliance with the requirements of publication and notice to the Solicitor General is mandatory.
Wang vs. Cebu City Civil Registrar: The Court emphasized that "undue embarrassment" or the mere desire to follow a stepfather's surname is not a sufficient ground for a judicial change of name. The state has an interest in the names of its citizens to prevent fraud and maintain the integrity of public records.

Summary Table of Legal Recourse

Situation	Recommended Legal Action	Legal Basis
Informal use of wrong surname (e.g., School)	Petition for Injunction / Specific Performance	Civil Code, Art. 26 & 364
False entry in Birth Certificate	Petition for Cancellation/Correction (Judicial)	Rule 108, Rules of Court
Seeking to legally change to Mother's name	Petition for Change of Name (Judicial)	Rule 103, Rules of Court
Correction of Clerical/Typo Error	Administrative Correction	Republic Act No. 9048

In the Philippines, the "best interest of the child" is the paramount consideration in all matters involving minors. However, the courts have consistently ruled that the best interest of the child is usually served by maintaining legal accuracy in the child's identity and preserving the child's link to both parents, unless compelling evidence suggests otherwise.