While this arrangement was legal by man's standard, God did not accept it. Therefore, John kept on telling Herod that it was not lawful for him to have Philip's wife. Because of this John was arrested, imprisoned and in time Herodias arranged John's execution. Another interesting facet of the marriage between Herod and Herodias is that they were not Jews, neither were they concerned about following God's law. Nevertheless they were amenable to God's law.
Many today live without regard to the moral standard of the Bible.
Like Herod and Herodias, all men everywhere are under God's law and will be judged accordingly. Jesus did not give the world a standard of morality that differs with the standard given to the church. Remember that Herod and Herodias both divorced and remarried according to the laws of the land. If it were the case that all divorce carries the right of remarriage, then Herod would not have uncovered the nakedness of his brother's wife, but the nakedness of Herodias. The reason Herod uncovered the nakedness of Philip's wife was because God did not recognize her divorce.