What is the ruling regarding a husband asking his wife to remove her niqab and suffice with the hijab, and does the wife have the right to refuse this request?

If the wife is convinced of wearing the niqab, it is not permissible for the husband to force her to remove it, especially if he married her while she was wearing it and consented to that. In this case, the wife is not considered disobedient (nashizah), for obedience is in what is good and not in disobedience to Allah.