In his book called Islamic Exceptionalism, Shadi Hamid explains that Christians have mostly been ambivalent about law and government.
That the Christian tradition seems ambivalent about law, governance and power is no accident…When Jesus died on the cross, he, in effect, released man from the burden of law. With the coming of Christ, salvation is achieved through faith in Jesus Christ rather than through observance of the law.
Christianity’s story of salvation is one of progression, with humanity passing through different states of spiritual development. Jewish or Mosaic law was provisional, meant for a particular time and place and for a particular chosen people, whereas Christianity was universal and everlasting…. The Mosaic Law was never intended to be either universal or eternally binding.
In short, it is not so much that Christianity has little to say about law, it that this ambivalence, or even opposition, to law was a feature of Christian theology during its early development.
In later centuries, Christian no doubt played a powerful role in public life, but this did not lead to legal development. As Ralston writes, “Simply put, there is nothing resembling a developed Christian account of public law in the New Testament.” This had important implications: “Christian theology, especially in the medieval period, primarily, divides ecclesial law from civil law into distinct sphere of society. Ecclesial laws govern the church and civil laws govern the public” (p.48)