Question

CAESAR: I must prevent thee, Cimber.
These couchings and these lowly courtesies
Might fire the blood of ordinary men,
And turn pre-ordinance and first decree
Into the law of children.

What is meant by " And turn pre-ordinance and first decree
Into the law of children"?

Answer 1

I think that Ceaser want to convey "if I revoke climber's brother then it will break law and the law made for all Romans will change into children's law.(means no one respect them and there existence will affect no-one and no one will care of them)

Answer 2

HeYa YoUr AnSwEr BeLoW

It means that Ceaser shall not change any laws  or orders that pre existed. "Law of children" means that it will be passed on to the future generation