This is what the Flock book (Elders Manual) has to say on page 135:
Courting or dating when one party is not free to marry is
wrong. (w80 8/1 pp. 30-1 ; w68 4/15 pp. 255-6)
Strong counsel and repeated warnings should be given,
and if the counsel is ignored, the individual(s) may be
marked. (2 Thess . 3 :14, 15)
When such action has escalated to the point where it has
become shocking and repeated efforts to help adjust the
situation have been ignored, there may be basis for taking
disfellowshipping action . (Gal . 5 :19; w83 3/15 p. 31 ;
w73 9/15 pp . 574-6)
If a person who has entered into an adulterous marriage is
eventually reinstated, it would be a rare case for him to
be recommended to serve in a responsible position in the
congregation, at least not until after the remarriage or
death of the mate he put away without Scriptural basis .