Christianity is based on the words of the gospel authors who wrote about what they heard, and Paul based on his subjective conversion experience.
Christianity is based on legal historical evidence of a risen Jesus Christ. Both protagonists and antagonists wrote about Him. I remember one Caesar claimed Jesus tricked people into believing He had been killed and raised. The problem with that is there were Roman government eye witnesses who saw Jesus dead; and in frustration stabbed Him with a spear. That's why the early manuscripts spread so much. They were read by someone who was a witness or knew someone who was a reliable witness.
I think you may be defining 'legal' somewhat loosely, to put it mildly.
Nobody would define the new testament as a legal document.
