WIW - illegal wedding?

SPOLIERS:












In the third Epoch 3, in the third chapter after Walter Hartwright resumes the narrative after Mrs Catherick's letter, Walter and the lovely but wet Laura get wed. I would have thought there was a legal impediment to the marriage in that, legally speaking, Laura Glyde (née Fairlie) was dead. Since the marriage banns could hardly be read out in Laura's parish in Limmeridge or her previous husband parish at Blackwater, Walter must have applied for a marriage licence. Since they were married in only ten days, that would confirm it. Legally speaking, is Walter married to Ann Catherick or was the wedding invalid and Walter's not married to anyone?