What's the difference between then and now?The main difference in the circumstances surrounding Edward VIII's decision to abdicate so he could marry Wallis Simpson and Charles' decision to not give up the throne when he married Camilla Parker Bowles is society and the perception of divorce.
Back in 1936, divorced people were not even allowed to be received at court in England. Although there was nothing in the British Constitution that prevented Edward VIII from marrying Wallis, the public sentiment against Wallis because of her two divorces created the need in Edward's mind that he should abdicate.
The text of Edward's radio announcement about his decision to abdicate, he states, "There has never been any constitutional difference between me and them, and between me and Parliament. Bred in the constitutional tradition by my father, I should never have allowed any such issue to arise."
Prince Charles made the decision that adverse public sentiment about his relationship with Camilla Parker Bowles was not enough to keep him from marrying her. Although his reputation appears to have been damaged by his openly adulterous affair with Camilla, Charles seems intent on keeping his right to the throne.