Hey genius, The Common Law wasn't from the 1600s, and it hasn't changed that much since it was first normalized sometime around the 12th century. Heck, there had been written versions for almost half a millenium prior to the 1600s. And The Common Law predates those first written codifications by at least another thousand years. The oldest documentation of the Common Law system was from the very first Christian missionaries to those lands, who noted that it was ancient when they arrived and found the system of law intriguing.
What, you think they invented Common Law in the 1600s? It had already been codified on paper (to the extent that Common Law is) before the Magna Carta. I think you've lost your grip on "historical fact". There is nothing "Christian" about English Common Law, it simply happens that the Common Law was fairly compatible with Christianity when that religion showed up later.