I wonder if by 'unite' you mean sexual intercourse or taking his part in some argument or dispute? Any adult in most western countries is free to engage in sexual activity with another consenting adult irrespective of whether either or both have commitments elsewhere, or whether anyone might be hurt by such encounter.
If you have sexual relations beofre the divorce comes through, then it surely ridicules the idea that the relationship (marriage) is over. If the divorce is already finalised, further sexually tinged incidents suggest that the relationship is ongoing, however unsatisfactorily.
If you mean unite, form a mutually cooperative agreement to defend or attack some issue, then there is nothing stopping you. However, this all sounds uncomfortably like unresolved business, a messy situation that you need to clarify. Are you divorced, or not?
Yes, you can unite with your husband after divorce; there is no law that states otherwise. People get back to their ex – spouse all the time. Many divorced couples have reunited and remarried after their divorce.
However, many factors determine whether a divorced couple will reunite. Keep in mind that your ex – spouse must be willing to reconcile with you for both of you to reunite. If your former spouse despises you and won’t have any contact with you, it would be difficult to reunite, it is best you move on with life. It takes the work of both people to reunite.