My child's father (US citizen) doesn't give consent for my son to get a citizenship of a country of my citizenship. I have a sole legal and physical custody and he has visitations on weekends. The court order says i need his consent only for traveling out of country. The embassy says that his rights are not terminated so they need his father's consent. And it's in child's best interest to get dual citizenship. Is it possible to sue the embassy or other legal ways that consulate agree not to request his consent?
If your national law says that you need father's consent, you need father's consent. As alternative, some national laws (for example, the Russian law) allows to obtain citizenship without parent's consent if child lives in this country. For example, if you is Russian citizen, you need parent's consent as long as you live in the United States. But as soon as you will relocate to Russia, his consent doesn't requires anymore.