What is the ruling of Islamic law regarding a wife traveling alone a distance ranging between 700-800 kilometers, and moving about alone in European cities, given that she wears the hijab and does not master the language of the country, and does the husband have the right to refuse in this case?

It is not permissible for a woman to travel except with her husband or a mahram. It is not the husband's right to allow his wife to travel without the company of a mahram, and he is not an oppressor if he prevents her in this situation; rather, he will be rewarded for it due to his compliance with the commands of Islamic law. This is an act of responsibility and concern for the wife's well-being. It is a grave error for the wife's mother to interfere by inciting her daughter to travel without a mahram. We advise you to handle the matter wisely and avoid discord.