Is resorting to child protection agencies and litigation in courts of non-Islamic countries to protect a Muslim child considered a violation of Sharia, especially if the mother refuses to resort to Sharia?

The principle is that a Muslim should only refer for judgment to the Shari'ah of Allah. However, it is permissible to refer to man-made laws under three conditions: if he cannot obtain his right except through this means, if he dislikes doing so, and if he does not take more than his due right.

Regarding the subject of the question, it is permissible for the divorced man to resort to foreign organizations to obtain custody of his son from his disbelieving ex-wife, and his refusal to withdraw the case is not considered a rejection of Allah's Shari'ah.

As for custody, if the mother returns to her country, her custody right is forfeited if she intends to travel for permanent residency. Custody is granted to the parent who is better in religion, and whoever neglects the religious upbringing of the child in custody should not be given custody. The divorced man should strive to obtain custody of his son as long as the mother travels and leaves him with his disbelieving grandmother.