In recent decades, family law has evolved to crystallize the “best interests of the child” as a key custody criterion. The French Civil Code, a model for systems including Iran, explicitly incorporates the child’s paramount interest in custody statutes. In Iran, after joining the CRC, the 2012 Family Protection Act prioritized the child’s best interests, though the criteria remain contested.

This research, through a comparative analysis of custody legislation in Iran and France and selected judicial rulings from both nations, seeks to answer: How have legislative approaches and judicial practices invoked and applied the child’s best interests in custody matters?

The analysis reveals that Iranian courts often use the principle to bypass age and gender limits on maternal custody, but many rulings still rely solely on these criteria, ignoring broader best interests considerations. French courts, in contrast, focus on securing the child’s rights through a discretionary assessment of their actual needs and circumstances.

Judicial rulings show that Iranian judges, influenced by a “doctrine of childhood” prioritizing maternal rights, have not sufficiently applied the supremacy of best interests over other factors. This has harmed children’s and sometimes mothers’ rights.

The study proposes several recommendations: Encourage judges to conduct a case-by-case assessment of best interests in all proceedings, consistent with international standards. Revise paternal guardianship powers to better protect the child’s rights. By aligning judicial practice with the principle’s core purpose, both systems can more effectively safeguard children as autonomous rights-holders in custody disputes.