If any spouse marrieis second time while first marriage is exisiting, it is an offence under IPC subject to the the personal laws of the person conserned. If he/She is not Muslim, he/she can be prosecuted in a criminal court.
If a person wants to marry while the spouse is livig, a divorce should be obtained. Divorce is granted by a court on valid grounds. A divorced person may remarry provided the decree has become final either by not being appealed against or by the appeal being dismissed.